Prepared in cooperation with the Arizona Department of Water Resources and Yavapai County

Simulation of Groundwater Withdrawal Scenarios for the Redwall-Muav and Coconino Aquifer Systems of Northern and Central Arizona

Scientific Investigations Report 2016–5115

U.S. Department of the Interior U.S. Geological Survey COVER Elevated, northwest-looking Google Earth view of Flagstaff, Arizona, in the foreground, the Coconino Plateau in the center, and Grand Canyon in the upper part of the image. Image Landsat from Google (2016). Simulation of Groundwater Withdrawal Scenarios for the Redwall-Muav and Coconino Aquifer Systems of Northern and Central Arizona

By D.R. Pool

Prepared in cooperation with the Arizona Department of Water Resources and Yavapai County

Scientific Investigations Report 2016–5115

U.S. Department of the Interior U.S. Geological Survey U.S. Department of the Interior SALLY JEWELL, Secretary U.S. Geological Survey Suzette M. Kimball, Director

U.S. Geological Survey, Reston, Virginia: 2016

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Suggested citation: Pool, D.R., 2016, Simulation of groundwater withdrawal scenarios for the Redwall-Muav and Coconino aquifer sys- tems of northern and central Arizona: U.S. Geological Survey Scientific Investigations Report 2016–5115, 38 p., http://dx.doi.org/10.3133/sir20165115.

ISSN 2328-0328 (online) iii

Contents

Abstract ...... 1 Introduction...... 2 Climate ...... 2 Vegetation...... 4 Land and Water Use...... 4 Regional Hydrogeology...... 4 Aquifer Geology and Structure...... 4 Aquifers...... 5 Proterozoic Basement...... 5 Redwall-Muav Aquifer...... 5 Coconino Aquifer...... 6 Alluvial Aquifers...... 6 Structure...... 6 Description of the Northern Arizona Regional Groundwater Flow Model...... 6 Withdrawal Scenarios...... 8 Water Uses...... 10 Scenario 1...... 14 Scenario 2...... 14 Scenario 3...... 15 Additional Scenario Assumptions...... 15 Small Private and Stock Well Withdrawals...... 15 Natural Recharge Rates...... 16 Incidental Recharge Rates...... 16 Drying of Model Cells During the Scenario Simulations...... 16 Simulated Effects of Withdrawal Scenarios...... 18 Initial Conditions for the Scenarios...... 18 Scenario Simulation Results...... 21 Simulated Changes in Water Levels...... 21 Scenario 1...... 21 Scenarios 2 and 3...... 21 Simulated Changes in Groundwater Discharge...... 25 Scenario 1...... 25 Scenarios 2 and 3...... 26 Model Limitations...... 27 Summary...... 28 References...... 30 Appendix 1...... 33 Appendix 2...... 35 Appendix 3...... 37 iv

Figures

1. Map of the area within the Coconino Plateau Water Advisory Council groundwater with- drawal scenarios...... 3 2. Conceptualized relations among major hydrogeologic units and the Northern Arizona Regional Groundwater-Flow Model layers...... 7 3. Graphs of projected groundwater withdrawals by major water users for future withdrawal scenarios...... 9 4. Map of the generalized groundwater-flow system initial conditions...... 11 5. Map of water-level change for scenario 1 in the uppermost model layer from 2006 through 2105 near the Coconino Plateau Water Advisory Council scenario region and sur- rounding areas, Arizona...... 22 6. Map of the difference in water-level change in the uppermost model layer compared with scenario 1 from 2006 to 2105 near the Coconino Plateau Water Advisory Council Sce- nario region and surrounding areas...... 23 7. Graph of sources of water, storage or surface-water flow and evapotranspiration, to a pumped well through time...... 26 8. Simulated changes in groundwater discharge to major perennial surface water features from 2006 through 2105 in and near the Coconino Plateau Water Advisory Council scenario region...... 27

Tables

1. Withdrawal wells that were not included in the original Northern Arizona Regional Ground- water Flow Model, installed after about 2005, and wells projected to be installed from 2006 through 2050...... 12 2. Projected and simulated incidental recharge rates at waste-water treament facilities in the Coconino Plateau Water Advisory Council Scenario region for three groundwater withdrawal scenarios...... 17 3. Simulated groundwater-flow budgets at the end of 2005 for selected regions of the Northern Arizona Regional Groundwater-Flow Model from Pool and others...... 19 v

Conversion Factors

SI to Inch/Pound Multiply By To obtain Length meter (m) 3.281 foot (ft) kilometer (km) 0.6214 mile (mi) Area square meter (m2) 0.0002471 acre hectare (ha) 2.471 acre square hectometer (hm2) 2.471 acre square kilometer (km2) 247.1 acre square meter (m2) 10.76 square foot (ft2) hectare (ha) 0.003861 square mile (mi2) square kilometer (km2) 0.3861 square mile (mi2) Volume cubic meter (m3) 35.31 cubic foot (ft3) cubic meter (m3) 0.0008107 acre-foot (acre-ft) cubic hectometer (hm3) 810.7 acre-foot (acre-ft) Flow rate cubic meter per second (m3/s) 70.07 acre-foot per day (acre-ft/d) cubic meter per year (m3/yr) 0.000811 acre-foot per year (ac-ft/yr) cubic hectometer per year (hm3/yr) 811.03 acre-foot per year (ac-ft/yr) meter per second (m/s) 3.281 foot per second (ft/s) meter per day (m/d) 3.281 foot per day (ft/d) cubic meter per second (m3/s) 35.31 cubic foot per second (ft3/s) cubic meter per day (m3/d) 35.31 cubic foot per day (ft3/d) Specific capacity liter per second per meter [(L/s)/m] 4.831 gallon per minute per foot [(gal/min)/ft] Hydraulic conductivity meter per day (m/d) 3.281 foot per day (ft/d) Hydraulic gradient meter per kilometer (m/km) 5.27983 foot per mile (ft/mi) Transmissivity* meter squared per day (m2/d) 10.76 foot squared per day (ft2/d) Leakance meter per day per meter [(m/d)/m] 1 foot per day per foot [(ft/d)/ft] vi

Temperature in degrees Celsius (°C) may be converted to degrees Fahrenheit (°F) as follows: °F=(1.8×°C)+32 Temperature in degrees Fahrenheit (°F) may be converted to degrees Celsius (°C) as follows: °C=(°F-32)/1.8 Vertical coordinate information is referenced to the insert datum name (and abbreviation) here, for instance, “North American Vertical Datum of 1988 (NAVD 88)” Horizontal coordinate information is referenced to the insert datum name (and abbreviation) here, for instance, “North American Datum of 1983 (NAD 83)” Altitude, as used in this report, refers to distance above the vertical datum. *Transmissivity: The standard unit for transmissivity is cubic foot per day per square foot times foot of aquifer thickness [(ft3/d)/ft2]ft. In this report, the mathematically reduced form, foot squared per day (ft2/d), is used for convenience. Specific conductance is given in microsiemens per centimeter at 25 degrees Celsius (µS/cm at 25°C). Concentrations of chemical constituents in water are given either in milligrams per liter (mg/L) or micrograms per liter (µg/L). NOTE TO USGS USERS: Use of hectare (ha) as an alternative name for square hectometer (hm2) is restricted to the measurement of small land or water areas. Use of liter (L) as a special name for cubic decimeter (dm3) is restricted to the measurement of liquids and gases. No prefix other than milli should be used with liter. Metric ton (t) as a name for megagram (Mg) should be restricted to commercial usage, and no prefixes should be used with it. Simulation of Groundwater Withdrawal Scenarios for the Redwall-Muav and Coconino Aquifer Systems of Northern and Central Arizona

By D.R. Pool

Abstract fields, and the towns of Tusayan, Williams, and Moenkopi. Water-level rises of 100 feet or more were simulated at areas The Northern Arizona Regional Groundwater Flow of incidental recharge near wastewater treatment facilities near Model was used to estimate the hydrologic changes, including Flagstaff, Tusayan, Grand Canyon South Rim, Williams, and water-level change and groundwater discharge to streams and Munds Park. springs, that may result from future changes in groundwater Simulated water-level change from 2006 through 2105 withdrawals in and near the Coconino Plateau Water Advisory for scenarios 2 and 3 is mostly different from water-level Council study area, Coconino and Navajo Counties, Arizona. change simulated for scenario 1 at the local level. For sce- Three future groundwater withdrawal scenarios for tribal and narios 2 and 3, water levels near Cameron in 2105 where nontribal uses were developed by the Coconino Plateau Water 1–3 feet higher than simulated for scenario 1. Water levels at Advisory Council and were simulated for the period represent- Moenkopi are more than 100 feet higher due to the elimination ing the years from 2006 through 2105. Scenario 1 assumes of a proposed withdrawal well that was simulated in scenario no major changes in groundwater use except for increased 1. Scenario 3 eliminates more groundwater withdrawals in the demand based on population projections. Scenario 2 assumes Flagstaff and Williams areas, simulates 1–3 feet less water- that a pipeline will provide a source of surface water from level decline than scenario 1 across much of the Coconino Lake Powell to areas near Cameron and Moenkopi that would Plateau, and water levels that are as much as 50 feet higher replace local groundwater withdrawals. Scenario 3 assumes than simulated by scenario 1 near withdrawal wells in the Wil- that the pipeline extends to the Flagstaff and Williams areas, liams and Flagstaff areas. and would replace groundwater demands for water in the area. Scenario 1 simulated the most change in groundwater The Coconino Plateau Water Advisory Council with- discharge for the Little Colorado River below Cameron and for Oak Creek above Page Springs where declines in discharge drawal scenarios primarily influence water levels and ground- 3 water discharge in the Coconino Plateau basin, near the of about 1.3 and 0.9 cubic feet per second (ft /s), respec- western margin of the Little Colorado River Plateau basin, tively, were simulated. Other simulated changes in discharge through 2105 in scenario 1 are losses of less than 0.4 ft3/s at and the Verde Valley subbasin. Simulated effects of the 3 withdrawal scenarios are superimposed on effects of previ- the Upper Verde River, losses of less than 0.3 ft /s at Havasu Creek and at Colorado River below Havasu Creek, losses ous variations in groundwater withdrawals and artificial and 3 incidental recharge. Pre-scenario variations include changes of less than 0.1 ft /s at Clear Creek, and increases in flow at the south rim springs and Chevelon Creek of less than 0.1 in water-levels in wells; groundwater storage; discharge to 3 streams and springs; and evapotranspiration by plants that use and 0.3 ft /s, respectively. Simulated changes in discharge groundwater. Future variations in groundwater discharge and for scenarios 2 and 3 are less than for scenario 1 because of water-levels in wells will continue to occur as a result of both lower rates of groundwater withdrawal. Scenario 3 resulted the past and any future changes. in greater groundwater discharge than scenarios 1 and 2 at Water-level variations resulting from post-2005 stresses, all major groundwater discharge features from 2006 through including groundwater withdrawals and incidental and 2105 except for Clear and Chevelon Creeks, where the same artificial recharge, in the area of the withdrawal scenarios groundwater discharge was simulated by each of the three are primarily localized and superimposed on the regional scenarios. changes caused by variations in stresses that occurred since Changes in groundwater discharge are expected to occur the beginning of the initial stresses in the early 1900s through after 2105 to all major surface features that discharge from 2005. Withdrawal scenario 1 produced a broad region on the the Redwall-Muav and Coconino aquifers because change Coconino Plateau where water-levels declined 3–5 feet by in aquifer storage was occurring at the end of the simulation 2105, and local areas with water-level declines of 100 feet or in 2105. The accuracy of simulated changes resulting from more where groundwater withdrawals are concentrated, near the Coconino Plateau Water Advisory Council groundwater the City of Flagstaff Woody Mountain and Lake Mary well withdrawal scenarios is dependent on the persistence of sev- eral hydrologic assumptions that are inherent in the Northern 2 Simulation of Groundwater Withdrawal Scenarios for the Redwall-Muav and Coconino Aquifer Systems of Arizona

Arizona Regional Groundwater Flow Model including, but not Land surface altitudes in the CPWAC study area range limited to, the reasonably accurate simulation of (1) trans- from more than 7,000 feet (ft) on San Francisco Mountain, missivity distributions, (2) distributions of vertical hydraulic the Mogollon Rim south of Flagstaff, and along the south properties, (3) distributions of spatial rates of withdrawal and rim of Grand Canyon to about 3,100 ft at the confluence of incidental recharge, (4) aquifer extents, and (5) hydrologic Beaver Creek and about 1,500 ft at the Colorado River west barriers and conduits. of Havasu Creek (fig. 1). North of the Mogollon Rim, the land surface generally slopes gently toward deep canyons at the Little Colorado and Colorado Rivers. To the south of the Mogollon Rim, the land surface drops more steeply to the Introduction Verde Valley. The analysis is restricted to the primary regional Red- The U.S. Geological Survey (USGS) Northern Arizona wall-Muav and Coconino aquifers that are accessed by the Regional Groundwater Flow Model (NARGFM; Pool and oth- major water users in the area. Other, more localized aquifers ers, 2011) was constructed for several purposes; one of which such as the Navajo Sandstone aquifer at Black Mesa, volcanic was to estimate the hydrologic changes—including changes rock aquifers near Flagstaff and Williams, and alluvial aqui- in water levels and groundwater discharge to streams, springs, fers along streams are not considered in the analysis and vegetation—that may result from future groundwater Springs and streams that discharge groundwater from withdrawals. The Coconino Plateau Water Advisory Council the regional aquifers of the area are included in this analysis. (CPWAC) would like to better understand the effect of future The major rivers in the study area (fig. 1) are the Colorado groundwater withdrawals from the primary aquifers that may River and Little Colorado River to the north of the Mogol- occur though the year 2105 and has developed three future lon Rim, and the Verde River to the south. The perennial withdrawal scenarios for testing using the NARGFM. This streams are largely supplied with groundwater discharge from report documents the changes in the groundwater-flow system springs, but flow is also supported by runoff from numerous simulated by the NARGFM from 2006 through 2105 using the intermittent and ephemeral streams. Groundwater discharge three scenarios. is also distributed along many stream reaches that gain flow. The analysis does not include the simulation of changes The primary perennial streams considered in this analysis in the groundwater system that may result from changes in cli- include the Colorado River, lower and middle parts of the mate and land-use. Past variations in recharge rates are known Little Colorado River, the Upper Verde River, and Oak Creek. to be important in the simulation of observed water-level Streams and springs that are tributaries of the Colorado River changes in the study area (Pool and others, 2011). The effects and are considered in the analysis include Havasu Creek and of land-use change on the groundwater system are largely several springs at the south rim of Grand Canyon. Streams unknown and not simulated by NARGFM. Only the ground- and springs that are tributaries of the Little Colorado River water effects caused by changes in groundwater withdrawals and are considered in the analysis include the lower peren- from the primary regional aquifers and associated changes nial parts of Clear Creek and Chevelon Creek. Oak Creek is a in incidental recharge from waste-water treatment facilities tributary of the Verde River. are simulated. By focusing only on the effects of changes in groundwater withdrawals, the CPWAC will be able to bet- ter assess changes in groundwater discharge and water levels Climate in wells that may result from each of the three withdrawal scenarios. Inclusion of climate scenarios that are beyond the The climate of the study area is primarily arid to semi- control of CPWAC would likely complicate the analysis and arid with large spatial and temporal variations of temperature were therefore avoided. and precipitation. Climate conditions are strongly correlated The study area is a small part of the region covered by with altitude; moderate summers and severe winters are at the NARGFM, which includes most of northern and central higher altitudes, and extreme summer heat and mild winters Arizona, but also adjacent parts of western New Mexico and are at lower altitudes. Microclimates are common in the study southern Utah. The areal extent of the analysis of the effects area because of local controls on the amount of solar radiation of the CPWAC withdrawal scenarios is the boundary of the and precipitation reaching the land surface in mountainous Coconino Plateau Partnership (fig. 1) and adjacent areas, terrain and in the deep canyons. which includes the Coconino Plateau and parts of the water- The spatial distribution of precipitation, derived from the sheds of the Verde and Little Colorado Rivers, and the western Basin Characterization Model of Flint and Flint (2008), is pri- part of Navajo County. The Coconino Plateau is a region of marily influenced by the direction of approaching winds and uplifted layered sedimentary rock overlain by layered volcanic orographic uplift of air masses. Average annual precipitation rocks and dissected by deep canyons. The layered sedimentary varies from about 7–15 inches in the basins, to about 20–37 rocks are deformed by faulting and uplift. In several alluvial inches in the mountains and higher altitudes of the Coconino basins drained by the Verde and Salt River systems, the defor- Plateau. Long term precipitation in the study area is domi- mation has resulted in thick accumulations of sediments. nated by extended below-average periods of precipitation Introduction 3

113° 112° 111°

37° MODEL ROWS

1-600 Page Kaibab Plateau 1-400 Coconino Plateau MODEL COLUMNS

Flagstaff Colorado DefianceUplift Plateau MogollonWinslow Holbrook Rim

NO-FLOW BOUNDARY

ver Kaibab Ri Havasu ARIZONA Cr Plateau eek rado olo Blue Springs C Complex Supai Tuba City

Black Moenkopi Grand Canyon Mesa 36° Village

Tusayan Coconino Plateau Cameron

basin Little Colorado River

L

i

t t

l Plateau e

Colorado basin

Valle T AUL

River AJO COUNTY V

MESA BUTTE F Red Lake N A

San Francisco COCNINO COUNTY Mountain YAV APAI Leupp COUNTY Williams Parks Flagstaff Winona Woody Mountain Lake Mary well field well field Winslow Big Chino 35° Verde Valley Red Gap sub-basin Ranch sub-basin Mogollan Rim well field eek Munds Cr Sedona Park eek Clear Oak Cr V er de River Creek

Beaver eek Little Cr Chino Prescott ClearCreek West sub-basin

Chevelon

County boundaries of the United States, USGS 2000 National Atlas, 1:2,000,000-scale resolution, 2002, USGS; Perennial streams from Arizona Department of Water Quality, 2015, Towns from USGS Geographic Names Information System, 1981. Coordinate System: NAD 1927 UTM Zone 12N. scale 1:100,000; Groundwater basin and sub-basin boundaries from Projection: Transverse Mercator. Datum: North American 1927. False Easting: 500,000.0000. False Northing: 0.0000. Arizona Department of Water Resources, 2008, scale 1:100,000; Central meridian: -111.0000. Scale factor: 0.9996. Latitude of origin: 0.0000. Units: meters Faults and folds from USGS SIR 2010–5180

EXPLANATION Town or landmark Coconino Plateau Partnership area Model layer 1 active extent Simulated stream ADWR Groundwater basin and subbasin boundary Model layer 2 active extent Perennial streams Coconino County boundary Model layer 3 active extent Major faults Folds 0 5 10 20 30 40 MILES

0 10 20 40 60 80 KILOMETERS Figure 1. Map of the area within the Coconino Plateau Water Advisory Council groundwater withdrawal scenarios, including Arizona Department of Water Resources (ADWR) groundwater basins, model layer extents, and inset map of Arizona showing Northern Arizona Regional Groundwater Flow Model model grid and boundaries. 4 Simulation of Groundwater Withdrawal Scenarios for the Redwall-Muav and Coconino Aquifer Systems of Arizona interspersed with occasional above-average periods of pre- Land and Water Use cipitation (Blasch and others, 2006). Annual precipitation is distributed between a summer monsoon period and a winter Population—The estimated population of Coconino frontal storms period. The summer monsoon (also known County was 136,539 in 2013 (U.S. Census Bureau, 2015), as the North American Monsoon, or the Southwestern, which includes most of the area of analysis. Arizona, or Mexican Monsoon), generally begins in early Land Use—Native American reservations account July and extends through September, and includes precipita- for about 68 percent of the lands in the Coconino Plateau tion from convective storms that are characteristically short Partnership study area. About 26 percent of the land in the lived (less than a few hours), but can be intense (precipi- area is publicly owned; 14 percent is managed by the U.S. tation greater than 1 in/hr), and localized (tens of square Department of Agriculture (USDA) Forest Service, 7 percent miles). The winter frontal season from November through is managed by the National Park Service, and 4 percent is March produces storms that are characteristically longer managed by the State of Arizona. Recreation, forest, cattle (12–48 hr), less intense (precipitation less than 0.25 in/hr), and sheep ranching, mining, and urban development are the and more regional in extent (hundreds of square miles) than largest land uses in the region. Privately held lands account summer convective storms. Precipitation also can fall during for about 7 percent of the total. October and November as a result of both tropical distur- Water Use—Groundwater (including spring water) bances from the southern Pacific Ocean and winter frontal withdrawals in the study area are primarily for industrial and storms from the north Pacific. Although precipitation during tribal/municipal/domestic water use. Near population centers, this period can be a substantial part of the annual total, the groundwater is supplied primarily by private and munici- atmospheric conditions that result in precipitation do not pal water companies. Wells are used in some rural areas to happen regularly. The average annual rainfall rate is greater obtain groundwater for domestic and stock use. Total well than the average annual snowfall rate for all climate stations withdrawals in the CPWAC area were about 12,500 acre-ft in the study area. The greater rainfall rate is attributed to during 2006–10. About 10,800 acre-ft were withdrawn from warm annual mean temperatures. This greater rate is true in the regional aquifers simulated by NARGFM on an annual the higher altitudes where the ratio of rainfall to snowfall is basis during 2006–10. About 1,700 acre-ft of the total were about 3 to 1, and in the basins where the ratio is greater. withdrawn from aquifers other than the regional aquifers Average annual temperatures range from about 68 °F in simulated by NARGFM. Surface water is also a water supply the basins to 43 °F at higher altitudes and are inversely cor- source at Page, Flagstaff, and Williams. A source of water related with altitude. Average annual minimum temperatures for Grand Canyon Village is spring discharge from the North were recorded as low as 36 °F on the north rim of the Grand Rim of Grand Canyon, which is imported to the study area Canyon and average annual maximum temperatures have through a pipeline. A portion of the water used for municipal, been measured as warm as 78 °F in the Verde Valley. Large tribal, and domestic purposes was returned to the primary differences between the minimum and maximum daily tem- regional aquifers as incidental recharge through waste-water peratures are characteristic of the area. treatment facilities and septic systems.

Vegetation Regional Hydrogeology The distribution of vegetation in the study area is influenced by temperature and by water availability. Thus, Descriptions of the regional hydrogeology of northern plant communities are distributed on the basis of differences Arizona include several elements—aquifers and confining in latitudes, altitudes, and topography. Basins along the units, rates and distribution of recharge, rates and distribu- Verde and Salt Rivers are inhabited by desert scrub char- tions of discharge, and groundwater flow through the aquifers acteristic of the Sonoran desert. Piñon-juniper woodlands between recharge and discharge areas. Each of the elements and chaparral are primarily present in the middle altitudes of hydrogeology are briefly discussed in this report. More (about 3,900–5,600 ft). The predominant type of vegetation complete descriptions of each element may be found in Pool at altitudes above 5,600 ft is montane coniferous forest on and others (2011) and in greater detail in numerous reports the Mogollon Rim and across a large region near the San for subregions of the study area. Francisco Mountain, Flagstaff, and Williams. Vegetation that taps groundwater supplies, phreatophytes, occur along perennial and intermittent streams. Important phreatophytes Aquifer Geology and Structure of the area include cottonwood, willow, sycamore, tamarisk, and mesquite. The stratigraphic sequence in the study area includes Proterozoic metamorphic and igneous rocks that are over- lain by a sequence of Cambrian to Permian sedimentary rocks. Late Tertiary volcanic rocks overlay the older rocks in places, especially along the Mogollon Rim. Sequences of late Regional Hydrogeology 5

Tertiary alluvial basin deposits, hundreds to thousands of feet Proterozoic Basement thick, overlie the older rocks in the alluvial basins along the Proterozoic metamorphic and igneous rocks form the Verde and Salt River drainages. A more complete description underlying confining bed for the Redwall-Muav, Coconino, of the rock units and aquifers of the study area can obtained and basin-fill aquifers, and, in general, do not store or trans- from Hart and others (2002), Leake and others (2005), Parker mit substantial amounts of water. Only in a few areas with and others (2005), Wirt and others (2005), Blasch and others significant fracturing is water found in quantities sufficient for (2006), Bills and others (2007), and Pool and others (2011). withdrawal. One of these areas is along the Inner Gorge of the Grand Canyon where several small springs and seeps dis- Aquifers charge from fractured Precambrian granites and metamorphic rocks. Most rock units in the study area contain some water- bearing zones. However, structural deformation has reduced Redwall-Muav Aquifer the continuity of saturated units across the study area. Groundwater systems of the study area are more complex The Redwall and Muav Limestones are the primary than is indicated by the fairly simple layering of the rocks that water-bearing rock units in the region of the Coconino Plateau, contain the groundwater systems. The complexity is because and underlie the Coconino aquifer in the remainder of the Col- of variations in stratigraphy, lithology, and geologic structure orado Plateau. Cooley (1976) defined the Redwall and Muav (Bills and others, 2007). Aquifers are briefly described here Limestone multiple-aquifer system as the saturated to partly but are described in greater detail in the NARGFM report saturated and hydraulically connected Redwall, Temple Butte, (Pool and others, 2011). Stratigraphic relations of the rock and Muav Limestones. Other regional studies have broad- units are shown in figure 7 of Pool and others (2011). The ened the extent of the aquifer to include several hydraulically Redwall-Muav aquifer (locally known as the R-M aquifer) connected limestone, sandstone, and shale units including the and the Coconino multiple aquifer system (locally known as Tapeats Sandstone, Bright Angel Shale, Muav Limestone, the C aquifer) are the primary aquifers in the study area. The Temple Butte Limestone, Martin Limestone, and Naco Forma- Redwall-Muav and Coconino aquifers are the primary regional tion (McGavock and others, 1986; Parker and others, 2005). aquifers on the Coconino Plateau in the study area (Cooley The Redwall Limestone occurs throughout the study area and and others, 1969; Cooley, 1976). Both the Redwall-Muav is the upper rock unit of the Redwall-Muav aquifer where aquifer and the Coconino aquifer have internal southeast- the Naco Formation is absent. The Temple Butte Limestone northwest trending groundwater divides that are coincident and the Muav Limestone underlie the Redwall Limestone with or near the Mogollon Rim, and divide the regional near the Grand Canyon in the area of the Coconino Plateau. groundwater-flow system into parts that flow northward South of the Grand Canyon, the Temple Butte Formation thins toward the Colorado and Little Colorado Rivers, and south- southward and overlies the Martin Limestone or is absent, and ward toward the Verde and Salt Rivers. Other local aquifers the Muav and Redwall Limestones are in direct contact. The lie adjacent to the regional aquifers and are hydraulically Martin Limestone is mainly in the central and southern part of connected including thick alluvial deposits in basins of the the plateau and thickens to the south. Verde River drainage system, thin stringers of Quaternary The Bright Angel Shale and Tapeats Sandstone under- alluvium along major streams, and fractured Proterozoic sedi- lie the Martin, Temple Butte, and Muav Limestones in the ments, granite, and metamorphic rocks that mainly occur in central and western parts of the study area. The Bright Angel upland areas (fig. 2). Other local aquifers that are hydraulically Shale is several hundred feet thick; however, it is not a major disconnected from the regional aquifer system and from each water-bearing unit because it is composed of very fine-grained other occur within Proterozoic rocks, the lower Supai Forma- sediments that impede the downward migration of water tion, the Coconino Sandstone, the Kaibab Limestone, volcanic (Huntoon, 1977). Nevertheless, dozens of springs discharge rocks, and Quaternary alluvium. These local, isolated aquifers from the Bright Angel Shale in Grand Canyon from fine generally are small and thus are unsuitable as long-term water grained sandstone, sandy siltstone, and bedding plane frac- supplies; however, these aquifers are used extensively to meet tures (Monroe and others, 2005). The Tapeats Sandstone is a local water demands. These local disconnected aquifers are major water-bearing unit in places. The Tapeats Sandstone is a taken into consideration in the regional groundwater-flow continuous unit along the south and north rims of Grand Can- system because groundwater that discharges from the local yon. South of Grand Canyon, the Tapeats Sandstone is mainly aquifers can percolate downward to the underlying regional present as isolated erosion remnants overlying Proterozoic aquifer system. The downward percolation of water from shal- rocks. The Tapeats Sandstone is believed to be hydraulically low local aquifers is an important process in the large region connected to the overlying Redwall and Muav Limestones covered by volcanic rocks in the Flagstaff, Williams, and through faults and fractures, and where the Bright Angel Shale much of the Mogollon Rim areas. is thin or absent. Groundwater primarily enters the Redwall-Muav aquifer through downward leakage from overlying units by way of faults, fractures, and other geologic structures that create 6 Simulation of Groundwater Withdrawal Scenarios for the Redwall-Muav and Coconino Aquifer Systems of Arizona secondary porosity and conduits for groundwater flow through of infiltrated streamflow to the underlying aquifer. Perched the lower Supai Formation, which is otherwise primarily a aquifers may form locally where the Quaternary alluvium over- confining unit. Groundwater flow in the aquifer is substantially lies low permeability rocks. enhanced by faults, fractures, and solution channels. Areas of substantial faulting and fracturing are (1) along the Mesa Butte Fault Zone; (2) across the Havasu Creek drainage basin from Structure Williams to Supai; (3) along the faults near Tusayan; (4) in Regional tectonic stresses have shaped the landscape of the Cameron area coincident with several large monoclines; the study area, disturbed the stratigraphic sequence, formed and (5) south of Flagstaff in association with extensional basins where sediments accumulated, and formed local zones basins (Cooley, 1976; Ulrich and others, 1984; Billingsley, of weakness that resulted in volcanism. These regional stresses 2000; Bills and others, 2000; Billingsley and others, 2006). have also influenced the groundwater-flow system through the The aquifer is anisotropic and confined in much of the study creation of faults and fractures that can locally be flow barriers area. Small parts of the aquifer are unconfined where the or conduits for groundwater flow. Northeast-, north-, and north- aquifer rocks crop out. Wells drilled along extension faults west-striking faults and other fractures dominate the structure and fractures typically penetrate zones of increased transmis- of the study area (Gettings and Bultman, 2005). Extensional sivity because of the solution-enhanced permeability (Errol L. stresses that have weakened the regional pre-Tertiary sediments Montgomery and Associates, 1999). have enabled large amounts of late Tertiary and Quaternary intrusive and volcanic rocks to reach the surface (Wolfe and Coconino Aquifer others, 1987a,b). In addition, zones of weakness are continuing The Coconino aquifer is the sequence of rock units to expand, lengthen, and deepen, in some areas into canyons, between the Moenkopi Formation and the lower Supai Forma- from continued interaction with water. Groundwater movement tion (McGavock and others, 1986; Bills and others, 2000, along the expanded zones of weakness enhances the preferen- 2007; Bills and Flynn, 2002). The primary water produc- tial flow paths through dissolution of carbonate rocks. ing unit is the Coconino Sandstone; however, the overlying Kaibab and Toroweap Limestones and the underlying Schne- bly Hill Formation and upper and middle Supai Formations Description of the Northern Arizona of the Supai Group can be locally major water producing units (Leake and others, 2005). The lower Supai Formation Regional Groundwater Flow Model typically forms a confining unit that separates the Coconino aquifer from the underlying Redwall-Muav aquifer and local The NARGFM was developed using the USGS ground- Proterozoic crystalline aquifers. West of the Mesa Butte Fault, water model MODFLOW-2000 (Harbaugh and others, 2000) the primary water-bearing zones of the Coconino aquifer are and MODFLOW-2005 (Harbaugh, 2005). The model grid locally present as perched aquifers (Bills and others, 2007) but includes 600 rows and 400 columns of finite-difference cells, are unsaturated across broad regions. The Coconino aquifer each 1-kilometer square, in the horizontal dimension. The thins toward the east, however the exact eastern boundary is model grid is rotated 60° in the counter-clockwise direction uncertain because water-level and geologic data are meager. about the geographic origin of the grid at Universal Transverse Groundwater in the Coconino aquifer is unconfined except Mercator zone 12 easting 660,000 m and northing 3,580,000 m. where the base of the Moenkopi Formation falls below the Rotation of the grid allows for row and column alignment with potentiometric surface across much of the region north of the the assumed principal directions of the hydraulic conductivity Little Colorado River. Many wells drilled into the confined tensor. The origin of the model grid lies at the outer corner of part of the aquifer flowed at land surface before significant the cell at row 600 and column 1. Model rows are incremented development of the groundwater supplies (Mann and Nem- from the cell at row 1, column 1 to row 600 in a southeasterly ecek, 1983; Mann, 1976). Groundwater flow in the Coconino direction. Model columns are incremented from the cell at aquifer is locally enhanced by fractures and faults (Bills and row 1, column 1, to column 400 in a northeasterly direction. others, 2000; Hoffmann and others, 2005; Kaczmarek, 2003; The model was constructed using units of meters for length Leake and others, 2005). and days for time. For this report, descriptions of values in the model are given in units of feet for length and days for time. Alluvial Aquifers NARGFM uses three model layers to simulate the primary hydrogeologic units across the model domain (fig. 2). Model Alluvial basin aquifers are present in basins that lie to layer 1 represents the upper part of the Coconino aquifer the south of the study area but are of minor importance in including the Coconino Sandstone and Kaibab Limestone the CPWAC study area. Alluvial aquifers of local importance and equivalent units in the Colorado Plateau structural prov- include thin stringers of Quaternary flood-plain alluvial and ince and adjacent areas, and the upper part of basin fill in the terrace deposits that occur along major streams. Where unsatu- alluvial basins of the transition zone. Model layer 2 represents rated, such as along perennial stream reaches, these highly the lower part of the Coconino aquifer including the upper and permeable deposits are effective conduits for the transmission Description of the Northern Arizona Regional Groundwater Flow Model 7 middle Supai Formation and equivalent units in the Colorado only where the primary hydrogeologic units are regionally Plateau structural province and adjacent areas, and the lower saturated in the Little Colorado River Plateau basin, primarily part of basin fill in the alluvial basins of the transition zone. in the region northeast of the Little Colorado River. The lower Model layer 3 represents the Redwall-Muav aquifer and older part of the Coconino aquifer is simulated as model layer 2 crystalline and sedimentary rocks where the Redwall-Muav where the upper and middle Supai Formations are regionally aquifer is absent across much of the transition zone and east- saturated in the area east of about Cameron and Williams. In ern part of the Colorado Plateau structural province. For more the Verde Valley, model layer 2 includes the saturated parts of detail, see Pool and others (2011). the upper and middle Supai Formations outside of the alluvial Boundaries of NARGFM include no-flow boundaries at basin, and the saturated part of the sand and gravel facies of the model margins and internal flow boundaries at perennial the Verde Formation in the alluvial basin. The Redwall-Muav streams. No-flow boundaries correspond with low perme- aquifer is simulated as model layer 3 throughout most of the ability rocks and groundwater divides, and constrain all of the region of the CPWAC withdrawal scenarios and surrounding simulated recharge in the model to flow toward discharge at areas except for a few areas where the Redwall-Muav aquifer internal flow boundaries and wells. Internal flow boundaries is absent and model layer 3 represents underlying rocks along are the primary controls that determine directions of ground- parts of the Colorado River. water flow. The distributions of internal flow boundaries Aquifer properties are represented in the NARGFM using relative to areas of variable flux at wells and recharge areas the Layer-Property Flow Package of MODFLOW. Impor- also partly determine the rates of change in discharge that tant aquifer properties included in the model are hydraulic result from the variable flux. The other important factors that conductivity, specific storage, and specific yield. Hydraulic determine rates of change are aquifer hydraulic and storage conductivity can be different in the two principal directions properties. of the model grid, along rows and columns. Directions and Within the area of the CPWAC withdrawal scenarios magnitude of primary hydraulic conductivity directions across and surrounding areas, the major simulated aquifers are the the area of the CPWAC withdrawal scenarios is influenced by Coconino aquifer and the Redwall-Muav aquifer. The upper geologic structure and secondary porosity. Model layer 3 is part of the Coconino aquifer is simulated as model layer 1 simulated with values along columns that are as much as 10

VERDE VALLEY SUB-BASIN COCONINO PLATEAU AND MOGOLLON RIM NARGFM MODEL LAYERS

MESOZOIC CONFINING BEDS QUATERNARY ALLUVIUM

Water table KAIBAB AND TOROWEAP FORMATIONS

LAYER 1 FLUVIO-LACUSTRINE UPPER BASIN FILL FACIES OF THE COCONINO SANDSTONE VERDE FORMATION

LOWER BASIN FILL UPPER AND MIDDLE SUPAI FORMATIONS LAYER 2 VOLCANIC ROCKS LOWER SUPAI FORMATION

REDWALL-MUAV LIMESTONE LAYER 3

PROTEROZOIC SEDIMENTS, GRANITE, AND METAMORPHIC ROCKS

Figure 2. Conceptualized relations among major hydrogeologic units and the Northern Arizona Regional Groundwater-Flow Model (NARGFM) layers.

AAXXXX_fig 01 8 Simulation of Groundwater Withdrawal Scenarios for the Redwall-Muav and Coconino Aquifer Systems of Arizona times the values along rows in the region for the Coconino the drain package is permanently removed from the simulated Plateau. Hydraulic conductivity for model layers 1 and 2 are flow system and not available to recharge through downstream simulated as equivalent along rows and columns across large stream reaches like in the stream package. The drain package regions, but variable in the area of the Mogollon Rim where is used to simulate streams and springs that have no important values along columns in some areas are as much as 5 times losing reaches. Important discharge features in the region of the values along rows. In the Oak Creek area, values along the CPWAC withdrawal scenarios that are simulated using the rows are locally 3 times greater than along columns. Mean stream package include the Verde and Little Colorado Rivers vertical hydraulic conductivity in all layers is lower than mean and major perennial tributary streams. Important discharge horizontal hydraulic conductivity along rows and columns. features that are simulated using the drain package include In MODFLOW, specific storage is applied where the aquifer the Colorado River, Havasu Creek, and several major springs is confined, as indicated by head or water level above the top in tributary streams. Input for the stream package includes of the aquifer. The product of specific storage and saturated specification of quantities for each of the stream reaches such thickness is the aquifer storage coefficient. The USGS has as the elevations of the top and bottom of the streambed, defined the storage coefficient of an aquifer as, “the volume streambed conductance, stream width, and Manning’s rough- of water it releases from or takes into storage per unit sur- ness coefficient. Input for the drain package includes the face area of the aquifer per unit change in the component of elevation and conductance of the spring or streambed. ET is head normal to that surface” (http://water.usgs.gov/admin/ simulated in riparian areas where there are shallow depths to memo/GW/gw55.28.html). The mechanisms for these storage the water table along the Verde and Little Colorado Rivers and changes are compression and decompression of the aquifer major perennial tributary streams. Input for each model cell skeleton and water. Similarly, specific yield is applied where where ET is simulated includes maximum ET rate, elevation the aquifer is unconfined, as indicated by head or water level of maximum ET rate, and maximum depth of ET. Maximum below the top of the aquifer. Specific yield is the quantity rates of ET assigned to model cells in the area of the CPWAC of water released per unit volume of the aquifer by gravity withdrawal scenarios and nearby regions were 6.54 × 10-4 ft/d. drainage from lowering the water table. The uppermost active Elevation of maximum rates of ET were assigned as 4.9 ft layer of the three model layers across the area of the CPWAC below the land surface in the model cell. Maximum depth of withdrawal scenarios is simulated as unconfined except in ET was simulated as 16.4 ft. For more details on representa- the eastern part of the area where the Moenkopi Formation is tion of features with the stream, drain, and ET packages in the an important regional confining unit overlying the Coconino NARGFM, see Pool and others (2011). aquifer. In areas where the uppermost active model layers 1 or 2 are simulated as unconfined, underlying model layers 2 and 3 are simulated as confined. Specific yield values for model layers 1 and 2 range from 0.10 to 0.20 in the area of the Withdrawal Scenarios CPWAC withdrawal scenarios. Low values of specific yield, Three future water demand scenarios (fig. 3, appendixes less than 0.02, are simulated for layer 3 where it is the only 1–3) for tribal and nontribal uses, including groundwater active model layer. withdrawals, were developed by the CPWAC for much of Saturated thickness also is an important factor in calcu- Coconino County, all of which lies within the area simulated lating groundwater movement in the model. Where heads are by the NARGFM. Projected withdrawal rates were developed below the top of the model layer, saturated thickness is the dif- for each decade from 2006 to 2105 for all three scenarios ference between the model-calculated head or water level and on the basis of population projections supplied by tribal the specified bottom of the aquifer. Mean saturated thickness is and nontribal agencies. For the scenario simulations, future much larger in layers 2 and 3 than in layer 1 in the area of the withdrawals are assumed to derive from existing exempt and CPWAC withdrawal scenarios and surrounding areas. nonexempt wells and many new withdrawal wells that are Discharge of groundwater in NARGFM is simulated as anticipated to be developed in several areas (fig. 4, table 1). occurring naturally along streams and springs simulated with The simulations also include estimated changes in incidental the stream (Prudic, 1989) and drain packages (Harbaugh, recharge of effluent from sewage plants and golf courses. 2005), and through evapotranspiration (ET). The stream The simulated scenarios do not included demands on water package keeps track of available flow and calculates stream supplies that are not simulated by NARGFM such as surface stage in each section or reach of stream that crosses a model water supplies and groundwater supplies from aquifers that are cell. If leakage of water from the stream exceeds available disconnected from the regional aquifers, including the Navajo, streamflow, no further leakage is allowed from downstream Dakota, and other shallow aquifers. reaches until the point where there is additional water avail- The scenarios include projected groundwater withdraw- able to the downstream reaches from tributary inflow or flow als from the primary regional aquifers by major water users of groundwater into the stream. The stream package is used for each decade from 2010 to 2049 followed by a 55-year to simulate discharge to streams that have significant reaches period of stable withdrawals from 2050 to 2105. Groundwater where streamflow infiltrates the channel and recharges the withdrawals are simulated from only the regionally extensive aquifer. Groundwater discharged at features simulated using Withdrawal Scenarios 9

30,000 A EXPLANATION 25,000 Other Williams, Valle, Tusayan Hualapai Tribe Navajo Tribe Hopi Tribe Communities near Flagstaff 20,000 Havasupai Tribe City of Flagstaff

15,000

10,000

5,000

0 30,000 B 25,000

20,000

15,000

10,000

Withdrawals, in acre-feet per year 5,000

0 30,000 C 25,000

20,000

15,000

10,000

5,000

0 2006–2009 2010–2019 2020–2029 2030–2039 2040–2049 2050–2105 Time, in years from 2006–2105

Figure 3. Graphs of projected groundwater withdrawals by major water users for future withdrawal scenarios. (A) Scenario 1, (B) Scenario 2, and (C) Scenario 3. SIRPool_fig 03 10 Simulation of Groundwater Withdrawal Scenarios for the Redwall-Muav and Coconino Aquifer Systems of Arizona

Coconino and Redwall-Muav aquifers and overlying locally to surface features such as streams, springs, and riparian extensive volcanic rock aquifers that likely discharge to the vegetation. This assumption is likely valid for the CPWAC underlying regional aquifers. Most of the wells, from which area because the rates of groundwater withdrawals in the area groundwater withdrawal for each scenario would be derived, are a small fraction of the overall water budget or recharge lie within two groundwater basins defined by the Arizona rates. This assumption would not likely be true for some local Department of Water Resources (ADWR)—the Coconino parts of the NARGFM where withdrawal rates are large in Plateau basin and the Little Colorado River Plateau basin. comparison to local groundwater budgets such as in the Little Some of the wells lie within the Verde Valley subbasin. Parts Chino. The CPWAC is most interested in the possible effects of Coconino County that were not included in the scenarios as of groundwater withdrawals for each scenario during the time demand areas are near Sedona in the Verde Valley subbasin, period through 2105. on the Mogollon Rim areas in eastern and southeastern parts of the County, and the Kaibab Plateau north of the Grand Canyon. Water Uses In addition to the withdrawal scenarios for the CPWAC Water use from wells that draw from the Redwall-Muav area, non-CPWAC area groundwater withdrawals and related and Coconino aquifers in the CPWAC scenarios is categorized incidental recharge also need to be included in the simulations. as tribal and nontribal. Annual tribal withdrawals from these For each of the three scenarios, non-CPWAC groundwater aquifers were less than 10 percent of the nontribal withdrawals withdrawals were assumed to remain unchanged from the rates prior to 2010. The scenarios anticipate that annual withdrawals simulated during the final NARGFM stress period, 2000–05. by the tribes will increase faster than the nontribal withdraw- This assumption recognizes that past and future non-CPWAC als during 2010–50, but will remain less than 20 percent of withdrawals will have future effects on the hydrologic features nontribal annual withdrawals. of interest in the CPWAC area, and simulates the effects of The largest pre-2010 tribal uses derived from the those withdrawals and incidental recharge. This assumption Redwall-Muav and Coconino aquifers primarily include also facilitates the evaluation of groundwater management groundwater withdrawals of a few hundred acre-feet per year practices within the CPWAC area separate from change caused (ac-ft/yr) from the Coconino aquifer for the Navajo Tribe in by practices outside of the area of interest. areas near Leupp, Cameron, Bodeway, and at Twin Arrows The intent of the scenario simulations is to evaluate Casino west of the City of Winslow. Other pre-2010 tribal uses changes in water levels in the regional aquifers and changes in include less than 200 ac-ft/yr from the Redwall-Muav aquifer groundwater discharge to streams and springs that may result for the Havasupai Tribe in the western part of the Coconino from possible future variations in groundwater withdraw- Plateau and less than 10 ac-ft/yr from nonregional aquifers als in the CPWAC area. Future changes, however, will also for the Hualapai Tribe in the western part of the Coconino result from past and future variations in recharge rates and Plateau. The scenarios anticipate the most potential growth, groundwater withdrawals in areas both within and outside of more than 3,000 ac-ft/yr by 2050, in tribal withdrawals from the CPWAC area. These past changes that affect future change the Coconino aquifer in the area to the south of Leupp, on the make the interpretation of the scenario results more complex. Navajo Nation. Other tribal withdrawals from the Redwall- In order to simplify the scenario results, it was advantageous Muav and Coconino aquifers are anticipated to increase to to eliminate the effects of past recharge variations from the about 205 ac-ft/yr by 2050. New wells are also anticipated analysis. Therefore, the effects of past recharge variations are to tap the Redwall-Muav aquifer for the Havasupai Tribe, eliminated from this analysis by simulating pre-2006 condi- increasing use to 25 ac-ft/yr, and the Hualapai Tribe, increas- tions using an average-annual recharge rate and using those ing use to 10 ac-ft/yr. Pre-2010 groundwater supplies for the 2005 ending conditions as the initial conditions for the sce- Hopi Tribe were primarily derived from the Navajo aquifer, narios. Additional scenarios other than those simulated, would which is not simulated in the NARGFM. However, a new be required to evaluate the post-2005 changes that result from well is anticipated to derive as much as 170 ac-ft/yr from the pre-2006 variations in withdrawals and recharge throughout Coconino aquifer near Moenkopi for Hopi Tribe use. the model area, future variations in withdrawal rates outside The largest users of groundwater from the Coconino and of the CPWAC area, and the effects of future variations in Redwall-Muav aquifers in the scenario area are nontribal. recharge rates. Several thousand acre-feet per year are withdrawn for use by Change resulting from variations in groundwater with- the City of Flagstaff and several water companies near Flag- drawals and incidental recharge for both past conditions and staff, the City of Williams, and other communities including future variations in each CPWAC scenario is determined Tusayan, Valle, and Grand Canyon Village. The City of Flag- by comparing the changes in water levels and groundwater staff withdraws the greatest amount of groundwater in the area discharge resulting from each scenario. This type of analysis and derives its supply mostly from the Coconino aquifer in the requires an assumption of a linear system response in the area Woody Mountain well field, Lake Mary well field, and local of interest throughout the simulation for each of the scenarios. wells within the city limits, which is known as the Local well Nonlinear changes that may occur include significant changes field (fig. 4). Groundwater is also withdrawn by Flagstaff from in the saturated thickness of aquifers and changes in discharge Withdrawal Scenarios 11

113° 112° 111°

37° 0 5 10 20 30 40 MILES 5200 4800 0 10 20 40 60 80 KILOMETERS Page 4400

4000

3600

3200 G

4800 6400

8000 2800 7200 2400

2000 7600 6000 3200 5200

2000 4000 4400 6800

er Havasu 5600 iv G R G G G Cr 3600 rado olo eek C G GG Blue Springs Supai G G GG 2800 G G 4000 2400 GG Tuba City 2400 4400GG G Moenkopi Grand Canyon G 36°

Village4800 Coconino 5200 Tusayan Little Colorado River 4400 Plateau Cameron basin 4000 3600 3600 Plateau

Fraziers Well basin

L i

Gray Mountain t

t

l e

Colorado 4000 Valle

Flagstaff River 4400 local well field Red Lake

3600

3600 Flagstaff Leupp Big Chino Fort Rock sub-basin Williams Winona sub-basin 4400 Parks 4400 6400

Woody Mountain Leupp Corner Mountainaire well field 6400 Winslow 35° Verde Valley Lake Mary 4800 6800

4800 well field 5600 sub-basin Munds Park Red Gap Verde River 5200 G Ranch Fox Ranch well field 5200 eek 6400 Sedona 6800 3600 eek Oak Cr Cr G 5600 G 4800 5200 G G Creek Clear eek Little 4800 6000 Cr 4000 Beaver Chino 5200 5200 G Prescott 3200 sub-basin 3200 ClearCreek est 6400 W Chevelon

County boundaries of the United States, USGS 2000 National Atlas, 1:2,000,000-scale resolution, 2002, USGS; Perennial streams from Arizona Department of Water Quality, 2015, Towns from USGS Geographic Names Information System, 1981. Coordinate System: NAD 1927 UTM Zone scale 1:100,000; Groundwater basin and sub-basin boundaries from 12N. Projection: Transverse Mercator. Datum: North American 1927. False Easting: 500,000.0000. False Arizona Department of Water Resources, 2008, scale 1:100,000; Northing: 0.0000. Central meridian: -111.0000. Scale factor: 0.9996. Latitude of origin: 0.0000. Units: meters Faults and folds from USGS SIR 2010–5180

EXPLANATION Town or landmark G Spring simulated using the MODFLOW Drain Package (DRN) Post-2005 wells added for CPWAC Scenarios 2006 water-level altitude in uppermost model layer, contour interval = 400 feet Simulated incidental recharge at WWTFs Stream simulated using the MODFLOW Drain Package (DRN) Simulated incidental recharge at golf course Stream simulated using the MODFLOW Stream Package (STR) Well included in NARGFM and CPWAC Scenarios Perennial streams Coconino County boundary Groundwater basin and subbasin boundary Coconino Plateau Partnership area Figure 4. Map of the generalized groundwater-flow system initial conditions, including existing and projected withdrawal wells and the Arizona Department of Water Resources (ADWR) groundwater basins in the region of the Coconino Plateau Water Advisory Council (CPWAC) groundwater withdrawal scenarios. WWTF, waste-water treament facility. 12 Simulation of Groundwater Withdrawal Scenarios for the Redwall-Muav and Coconino Aquifer Systems of Arizona

Table 1. Withdrawal wells that were not included in the original Northern Arizona Regional Groundwater Flow Model, installed after about 2005, and wells projected to be installed from 2006 through 2050. [Well locations are in North American Datum of 1927 coordinate system, in both Universal Transmercator (UTM) Zone 12 coordinates (meters) and geographic coordinates of latitude and longitude (degrees, minutes, and seconds)].

Well name UTM Easting UTM Northing Latitude Longitude Model layer A-1 Mountain Sub-1 deep 432502 3895252 35° 11' 59.21" N 111° 44' 29.30" W 2 Anasazi Water Co. 398755 3981129 35° 58' 16.08" N 112° 07' 22.42" W 3 Bellmont Flagstaff Meadows 427261 3898447 35° 13' 41.60" N 111° 47' 57.57" W 2 Bellmont A-22-05 36CCC shallow 424956 3899850 35° 14' 26.53" N 111° 49' 29.20" W 3 Bellmont A-22-05 36CCC deep 424956 3899851 35° 14' 26.56" N 111° 49' 29.20" W 3 Bellmont A-21-06 06CBA 426781 3898834 35° 13' 54.04" N 111° 48' 16.68" W 3 Bodaway/Gap 464329 3983982 36° 00' 05.25" N 111° 23' 44.81" W 1 Bodaway/Gap 459482 3977509 35° 56' 34.47" N 111° 26' 57.22" W 1 Cameron 1, NTUA wells 460796 3976325 35° 55' 56.23" N 111° 26' 04.56" W 1 Cameron 2, BIA wells 459194 3968986 35° 51' 57.79" N 111° 27' 07.14" W 1 Canyon Mine 401100 3971500 35° 53' 04.46" N 112° 05' 44.49" W 3 Cedar Valley Water Co. (3 wells)1 462246 3893699 35° 11' 14.41" N 111° 24' 52.82" W 2 Flagstaff Local well field (Dog- 445420 3893556 35° 11' 06.99" N 111° 35' 58.07" W 2 pound) Flagstaff Local well field (I40tp) 443025 3894348 35° 11' 32.22" N 111° 37' 32.96" W 2 Flagstaff Local well field (Inter- 446253 3897563 35° 13' 17.22" N 111° 35' 26.07" W 2 change) Flagstaff Local well field (Shop) 448675 3898375 35° 13' 44.03" N 111° 33' 50.45" W 2 Flagstaff Local well field(Fort 437162 3889464 35° 08' 52.42" N 111° 41' 23.44" W 2 Tuthill) Flagstaff Local well 436453 3894641 35° 11' 40.30" N 111° 41' 52.89" W 2 field(Stonehouse) Flagstaff Local well field(Sinagua) 445267 3894261 35° 11' 29.84" N 111° 36' 04.28" W 2 Flagstaff Lake Mary well field 445670 3885700 35° 06' 52.02" N 111° 35' 46.32" W 2 Flagstaff Ranch Golf Course 18 435691 3892397 35° 10' 27.29" N 111° 42' 22.40" W 2 Flagstaff Ranch Golf Course 6 436093 3893000 35° 10' 46.96" N 111° 42' 06.67" W 2 Flagstaff Ranch Golf Course 7 435691 3893000 35° 10' 46.87" N 111° 42' 22.57" W 2 Flagstaff Ranch Golf Course 8b 435389 3892296 35° 10' 23.94" N 111° 42' 34.31" W 2 Flagstaff Red Gap Ranch A-20-13 507505 3884686 35° 06' 24.28" N 110° 55' 3.54" W 1 0 25CAA Flagstaff Red Gap Ranch A-20-13 504091 3885888 35° 07' 03.37" N 110° 57' 18.38" W 1 0 22CDB Flagstaff Red Gap Ranch A-20-14 508913 3889105 35° 08' 47.69" N 110° 54' 07.75" W 1 0 07CDB Flagstaff Red Gap Ranch A-20-13 506102 3886279 35° 07' 16.02" N 110° 55' 58.91" W 1 23DBB Flagstaff Red Gap Ranch A-20-13 502282 3886277 35° 07' 16.02" N 110° 58' 29.84" W 1 21CBA Flagstaff Red Gap Ranch A-20-13 499649 3886078 35° 07' 09.57" N 111° 00' 13.86" W 2 19DBC Flagstaff Red Gap Ranch A-20-13 504495 3884888 35° 06' 30.90" N 110° 57' 02.43" W 1 27ACC Flagstaff Red Gap Ranch A-20-14 509118 3883064 35° 05' 31.57" N 110° 53' 59.88" W 1 31CAA Flagstaff Red Gap Ranch A-20-13 506702 3883883 35° 05' 58.23" N 110° 55' 35.28" W 1 35AAA Withdrawal Scenarios 13

Table 1. Withdrawal wells that were not included in the original Northern Arizona Regional Groundwater Flow Model, installed after about 2005, and wells projected to be installed from 2006 through 2050.—Continued.

Well name UTM Easting UTM Northing Latitude Longitude Model layer Flagstaff Red Gap Ranch A-19-14 511137 3882002 35° 04' 57.03" N 110° 52' 40.19" W 1 05ABD Flagstaff Red Gap Ranch A-20- 497998 3886506 35° 07' 23.45" N 111° 01' 19.09" W 2 12.5 13ACB Flagstaff Red Gap Ranch A-20-13 508308 3885086 35° 06' 37.24" N 110° 54' 31.80" W 1 25ADA Flagstaff Red Gap Ranch A-20-13 501283 3885485 35° 06' 50.31" N 110° 59' 09.31" W 2 29ABB Fort Valley Deep wells (2 wells)1 434568 3902920 35° 16' 08.61" N 111° 43' 09.80" W 2 Fox Ranch 441607 3860447 34° 53' 11.43" N 111° 38' 20.45" W 2 Fox Ranch 438647 3858713 34° 52' 14.53" N 111° 40' 16.57" W 2 Gray Mountain 457438 3955623 35° 44' 43.78" N 111° 28' 14.59" W 1 Hopi Tribe at Moenkopi 481648 3996540 36° 06' 54.58" N 111° 12' 14.09" W 1 Howard Mesa 382088 3969930 35° 52' 05.93" N 112° 18' 21.76" W 1 Hualapai Tribe 277150 3931987 35° 30' 29.74" N 113° 27' 25.69" W 3 Leupp PW-1A 490306 3892082 35°10’ 24.31’’ N 111° 06’23.26’’ W 1 Leupp PW-2B 496398 3895436 35° 12’ 13.32” N 111° 02’ 22.45” W 1 Leupp PW-3 505425 3891201 35° 09’ 55.84’’ N 110° 56’25.55’’ W 1 Parks Deep well 413022 3901950 35° 15' 31.22" N 111° 57' 22.13" W 3 Patch Karr 397644 3946454 35° 39' 30.36" N 112° 07' 50.78" W 3 Supai Hilltop well 350319 4000488 36° 08' 21.74" N 112° 39' 48.92" W 3 Tusayan 1 398149 3980826 35° 58' 06.02" N 112° 07' 46.47" W 3 Tusayan 2 398345 3981395 35° 58' 24.55" N 112° 07' 38.91" W 3 Valle 1 396215 3945062 35° 38' 44.64" N 112° 08' 46.96" W 3 Valle 2 396014 3944861 35° 38' 38.04" N 112° 08' 54.85" W 3 Winona Casino 461850 3894911 35° 11' 53.70" N 111° 25' 08.68" W 2 Williams A-22-02 28BAD 391995 3902794 35° 15' 51.24" N 112° 11' 14.52" W 3 Bearizona A-22-22 06BBA 395002 3901505 35° 15' 10.55" N 112° 09' 14.94" W 3 1More than a single well may be constructed in the vicinity of the site. The projected withdrawal rate from all wells, shown in appendixes 1–3, is simulated at a single well rather than multiple wells, which is unlikely to produce significantly different simulated results of regional water-level change or capture of nearby surface water features. wells and springs that flow from glacial outwash and volcanic be withdrawn to meet the Designated Adequate Water Supply, rocks within the inner basin of San Francisco Mountain. The a maximum annual withdrawal rate determined by the State of scenarios anticipate that future City of Flagstaff groundwa- Arizona Department of Water Resources. Other communities ter supplies will continue to be derived from the same areas, near Flagstaff that use groundwater from the Coconino aquifer but augmented with new wells that tap the Coconino aquifer include Bellmont, Doney Park (including Timberline and within city limits and at the Red Gap Ranch well field about Fernwood areas), Flagstaff Ranch, Forest Highlands, Kachina 10 miles west of Winslow. Total withdrawals by the City are Village/Mountainaire, Winona, Coconino Estates, Munds currently capped at 9,913 ac-ft/yr from the existing sources Park, and Parks. Additional withdrawal wells are projected to based on an Adequate Water Supply Determination from be developed near many of these communities, at Fox Ranch ADWR (Erin Young, hydrologist, City of Flagstaff, written south of Flagstaff, and near Cameron to the north of Flagstaff. commun., 2014). Additional supplies from the new Red Gap The City of Williams is expected to develop new withdrawal well field will be capped at 8,000 ac-ft/yr by agreement with wells in the Redwall-Muav aquifer. New withdrawal wells the Navajo Nation (Erin Young, hydrologist, City of Flagstaff, in the Redwall-Muav aquifer are also expected to be devel- written commun., 2014). Maximum withdrawal rates for the oped near the communities of Tusayan, Valle, Red Lake, and City of Flagstaff for the scenarios are about 15,000 ac-ft/yr Gray Mountain. All nontribal water demands included in the during 2051–2105, although as much as 16,500 ac-ft/yr may CPWAC scenarios assume a 20 percent water conservation 14 Simulation of Groundwater Withdrawal Scenarios for the Redwall-Muav and Coconino Aquifer Systems of Arizona

(Bureau of Reclamation, 2006) over conditions prior to 2010 Havasupai Tribe withdrawals from the Redwall-Muav aquifer for the duration of the simulated period. near the western margin of the NARGFM region are projected Many private wells withdraw small amounts of water to increase only slightly, from about 170 ac-ft/yr before 2010 for domestic and stock use throughout the scenario area. to 200 ac-ft/yr in 2050. Hualapai Tribe withdrawals from Most of these wells draw water from groundwater in vol- the Redwall-Muav aquifer near the western margin of the canic rocks and other perched water-bearing zones. A few NARGFM region are projected to increase slightly to only of these wells, however, do draw water from the Coconino about 10 ac-ft/yr by 2050. aquifer. The withdrawal scenarios include estimates of Nontribal demand for water will occur mostly in Flagstaff future withdrawals for the private wells, but only at the and in surrounding areas including the Williams, Valle, and wells existing in 2005. Total simulated withdrawal rates for Tusayan areas, the region between Winslow and Leupp, and these wells was about 500 ac-ft/yr during 2000–05 in the as far south as Munds Park (fig. 1). The City of Flagstaff will NARFGM model. The private well withdrawals are divided continue to develop new wells in the inner city area, including into three regions for the scenarios, including the corridor the Local well field, and at Red Gap Ranch, which could be between Flagstaff and Williams, the corridor between Wil- supplying water to the city by 2020. Groundwater develop- liams and Grand Canyon National Park, and all remaining ment for projected nontribal water demands in the Williams, areas. About 50 percent of these well withdrawals are in the Valle, and Tusayan areas will come from the Redwall-Muav Flagstaff to Williams corridor and about 25 percent of the aquifer. The City of Williams is capped at development of withdrawals are in each of the other two areas. 700 ac-ft/yr from its existing wells in the Redwall-Muav aquifer south of Williams by an agreement with ADWR (Den- nis Wells, Williams City Manager, oral commun., 2007). That Scenario 1 limit is projected to be nearly attained at 675 ac-ft/yr by about 2050. Additional demands on the Redwall-Muav aquifer in Scenario 1 assumes that all water demand will be met the region between Williams and Grand Canyon are depen- by continuing individual, tribal, and municipal groundwater dent on if, and how, Grand Canyon National Park resolves its development and that there will be no regional water project maintenance and (or) replacement issues with the trans-canyon to bring a combination of surface-water and groundwater pipeline that delivers water from Roaring Springs on the north resources to meet water use demands in the CPWAC region rim to the south rim, and future development at Tusayan and by 2050. Scenario 1 has the most groundwater withdraw- Valle. als of the three scenarios as withdrawals for each major Most of the projected increases in nontribal withdrawals groundwater user or group of users are projected to increase occur in the vicinity of Flagstaff and nearby communities. City throughout the scenario. Total groundwater withdrawals of Flagstaff withdrawals, including withdrawals at Red Gap from the Redwall-Muav and Coconino aquifers within the Ranch, increase from about 7,000 ac-ft/yr before 2010 to about CPWAC region for scenario 1 increase from about 15,000 ac-ft/yr in 2050. Flagstaff withdrawals are distributed 10,800 ac-ft/yr during 2006–10 to about 25,300 ac-ft/yr among the existing wells at the Woody Mountain, Lake Mary, beginning in 2050 (fig. A3 , appendix 1). Not included in the and Local well fields, the inner basin area of San Francisco scenario are about 7,400 ac-ft/yr of groundwater withdraw- Mountain, and new wells at Red Gap Ranch. Reduced with- als from the N aquifer for tribal use. drawals at the Lake Mary well field of about 900 ac-ft/yr in Under this scenario the tribal demand for water will 2010 are partly replaced by increases in withdrawals from the grow to a rate of 160 gallons per day per capita as tribal Local well field. Increases in City of Flagstaff withdrawals communities improve their infrastructure. Most of this new after 2019 will be sourced from wells at the Woody Mountain, demand will be met by development of existing and new Local, and Red Gap Ranch well fields, including increases of Coconino aquifer wells in the Leupp area. New Coconino about 1,300, 2,300, and 4,300 ac-ft/yr, respectively, by 2050. aquifer wells will also be drilled in the area of Moenkopi. Withdrawals for several other communities near Flagstaff are Other tribal demands for groundwater in the western part projected to increase from about 2,100 ac-ft/yr before 2010 to of the model domain for the Hualapai and Havasupai about 3,800 ac-ft/yr in 2050. Withdrawals from stock, domes- Tribes will be minor and developed from the Redwall- tic, and small industrial wells are projected to increase from Muav aquifer. Withdrawals from the Coconino aquifer near about 500 to 1,600 ac-ft/yr by 2050, with about 50 percent Cameron and Bodaway for the Navajo Tribe are projected of the increase occurring in the region between Flagstaff and to increase during 2010–50 from about 170 to 750 ac-ft/yr Williams. and 200 to 820 ac-ft/yr, respectively. Navajo Tribe with- drawals from the Coconino aquifer at and near Leupp are projected to increase from about 200 to 1,000 ac-ft/yr for Scenario 2 the same period with the addition of several new wells. Withdrawals for the Hopi Tribe are projected to begin from Scenario 2 assumes that the proposed Western Navajo the Coconino aquifer near Moenkopi before 2020 at a rate Pipeline will provide a source of surface water from Lake of about 30 ac-ft/yr and increase to 170 ac-ft/yr in 2050. Powell to the communities of Cameron, Tuba City, and Withdrawal Scenarios 15

Moenkopi, and all nontribal water demands will continue to be during 2030–2105 rather than the greater rates for scenarios 1 met by groundwater development. Under this scenario, there and 2. City of Williams withdrawals are eliminated after 2019. will be limited groundwater development of the Coconino Groundwater withdrawals by all private domestic, stock, and aquifer in the Leupp area to meet projected local demands. industrial wells are unchanged from scenarios 1 and 2. Overall Projected nontribal demands for water will be met by devel- groundwater withdrawals for scenario 3 during 2050 through opment of groundwater from the Coconino aquifer and the 2105 are about 4,300 ac-ft/yr less than those in scenario 1. Redwall-Muav aquifer as described in scenario 1. Total groundwater withdrawals from the Redwall-Muav and Coconino aquifers within the CPWAC region for sce- Additional Scenario Assumptions nario 2 increase from about 10,800 ac-ft/yr during 2006–10 to about 23,400 ac-ft/yr during 2050–2105 (fig. B3 , appendix 2). A few additional assumptions were required to complete Withdrawals for major groundwater users or group of users each of the groundwater withdrawal scenarios. Assump- increase throughout the scenario with the exception of use by tions were applied regarding distributions of withdrawals by the Navajo and Hopi Tribes, which increase at much reduced small private and stock wells and wells not considered in the rates in comparison to scenario 1 because of the elimination scenarios (outside of the CPWAC area of concern); rates of of groundwater withdrawals for tribal use from the Coconino natural, artificial, and incidental recharge; and how to treat aquifer near Cameron and Moenkopi. Similar to scenario loss of withdrawals that occur as a result of model cells that 1, most increases in groundwater withdrawals for scenario dry during the simulations. Withdrawals from aquifers not 2 result from increases in Flagstaff and nearby community included in the NARGFM were not considered in the sce- withdrawals. Withdrawals from stock, domestic, and small narios. This exclusion primarily included withdrawals from industrial wells are projected to increase to 1,600 ac-ft/yr, as the Navajo aquifer and overlying aquifers in the Black Mesa was assumed for scenario 1. Overall groundwater withdrawals area. Wells that withdraw water from local perched aquifers, for scenario 2 during 2050–2105 are about 1,900 ac-ft/yr less such as in volcanic rocks that overlie the regional Coconino than those in scenario 1. and Redwall-Muav aquifers, were not explicitly simulated in NARGFM. However, these local shallow aquifers were implicitly simulated by assuming discharge from them likely Scenario 3 flows into the underlying regional aquifers, and that withdraw- als from the shallow aquifers remove water that would other- Scenario 3 assumes that there will be a partnership wise recharge the regional aquifers. Withdrawals from shallow between the tribal and nontribal interests on the Coconino perched aquifers that overlie and discharge to the regional Plateau that make it possible to extend a part of the proposed aquifers were therefore included in the scenarios as withdraw- Western Navajo Pipeline onto the Coconino Plateau to supply als from the regional aquifers. projected unmet demands for water in this area by 2050. As part of an appraisal study by the Bureau of Reclamation for the CPWAC, the projected unmet demands for nontribal water Small Private and Stock Well Withdrawals on the Coconino Plateau were about 15,800 ac-ft/yr (Bureau Withdrawals from most small private and stock wells of Reclamation, 2006). All other nontribal water demands were assumed to vary in the future according to the sce- will continue to be met by groundwater development in the nario withdrawal category “Other domestic, stock and small Coconino and Redwall-Muav aquifers. industrial groundwater” (appendixes 1–3). Several additional Total groundwater withdrawals from the Redwall-Muav tribal and private wells were anticipated by CPWAC to be and Coconino aquifers within the CPWAC region for scenario added to this withdrawal category after 2005 (table 1) and 3 increase from about 10,800 ac-ft/yr during 2006–09 to about were assigned the withdrawal rates for the category “Other 20,900 ac-ft/yr during 2050–2105 (fig. C3 , appendix 3). domestic, stock and small industrial groundwater”. Addi- Withdrawals for major groundwater users or group of users tional private wells were included in the simulations for the increase throughout the scenario, but at rates that are much Canyon Mine located between Valle and Tusayan (fig. 4) and reduced in comparison to scenario 1. Similar to scenarios Bearizona Wildlife Park near Williams (appendixes 1–3). 1 and 2, most of increases in groundwater withdrawals for The uses of an estimated 44 ac-ft of groundwater withdraw- scenario 3 result from increases in Flagstaff and nearby com- als from the Redwall-Muav aquifer at the Canyon Mine are munities. The reduced rates of groundwater withdrawals to for the construction of the mine shaft during 2013–16, mining nontribal users would be offset by imported surface water. All during 2016–22, and reclamation activities during 2023–25. of the reduced withdrawals relative to scenario 2 are because Groundwater use at this site is scheduled to return to zero after of reduced groundwater withdrawals for the Cities of Flagstaff 2029. Annual groundwater withdrawals at Bearizona Wildlife and Williams after 2019. City of Flagstaff withdrawals are Park are estimated as about 120 ac-ft/yr beginning with a well reduced over scenarios 1 and 2 by maintaining withdrawal drilled in 2015. rates at the Local well field at 2020 rates of 2,500 ac-ft/yr 16 Simulation of Groundwater Withdrawal Scenarios for the Redwall-Muav and Coconino Aquifer Systems of Arizona

Natural Recharge Rates community throughout the simulation period for each sce- nario (table 2). Water demand and incidental recharge at two Natural recharge rates for the three simulated ground- facilities, Grand Canyon Village and Forest Highlands, was water withdrawal scenarios are assumed to occur at a con- assumed to remain unchanged through the scenario period. stant rate that is equivalent to average-annual rates of natural Demand and incidental recharge for the other 11 facilities was recharge simulated in NARGFM. Average recharge rates assumed to increase with projected demand. Total estimated applied to NARGFM were derived from the modified Basin incidental recharge of wastewater effluent increases from Characterization Model (BCM; Flint and Flint, 2008), which about 5,700 ac-ft/yr during 2006–09 to about 13,000 ac-ft/yr estimates direct monthly recharge that is calculated as the during 2050–2105. Most incidental recharge from wastewater remainder of precipitation after accounting for runoff, evapo- effluent is estimated to occur near the two City of Flagstaff ration, vegetation requirements, and retention of moisture by facilities, Rio De Flag and Wildcat Hill, which account for soils. The BCM estimates used in NARGFM were modified about 80 percent of the total estimated effluent recharge to include additional recharge through ephemeral channels within the CPWAC area throughout the scenario simulation in alluvial basins that are outside of the area of the CPWAC period. Estimated incidental recharge near the City of Flagstaff scenarios. No modifications of BCM recharge estimates were facilities increases from about 4,900 ac-ft/yr during 2006–09 made in the area of the CPWAC scenarios. to about 10,700 ac-ft/yr during 2050–2105. In comparison, total estimated incidental recharge near the other 11 facilities Incidental Recharge Rates increases from about 900 ac-ft/yr to about 2,400 ac-ft/yr over the same period. Additional assumptions were made regarding projected rates of incidental recharge within and outside of the CPWAC Drying of Model Cells During the Scenario scenario region. Incidental recharge occurs as a result of excess irrigation of golf courses and agricultural fields, and Simulations effluent discharged from waste-water treatment facilities Drying of model cells that include well withdrawals (WWTF). This assumption is consistent with the assumed outside of the scenario area was allowed to occur, resulting groundwater withdrawal rates outside of the CPWAC area in some areas where much of the withdrawals were elimi- that were previously discussed. For all sources of incidental nated during the scenarios. Fortunately, the withdrawal losses recharge outside of the CPWAC scenario region, simulated did not cause variations in the simulation results within the rates of incidental recharge for the period 2000–05 were area of CPWAC scenarios because the losses were outside of projected to remain at 2000–05 rates throughout the period the CPWAC area and common in rate and location for each of the scenario simulations. Incidental recharge from excess scenario. irrigation of golf courses and agriculture within the CPWAC Distributions of some withdrawals within the scenario scenario area was assumed to occur during the scenarios area were modified from the pre-2006 simulation for the at the same rate and locations that it occurred during the purpose of preventing drying of the pumped model cell and 2000–05 NARGFM simulation period. Incidental recharge allowing retention of the projected withdrawals throughout from discharge of effluent at 13 WWTFs were simulated in the the period of the simulation, including the locations of with- scenarios (table 2). Six of the WWTFs were simulated in the drawals at several wells near the Woody Mountain and Lake original NARGFM including Munds Park, Kachina Village, Mary well fields. Modifications included redistribution of the City of Williams, Supai Village, and two City of Flagstaff withdrawals to include deeper layers, and lateral translation facilities—Rio de Flag and Wildcat Hill (table 2). For the of wells to spread the collective cone of depression resulting scenario simulations, incidental recharge from an additional from a concentrated area of well withdrawals. Withdraw- 7 WWTFs were included in the scenario simulations includ- als from all wells at the Woody Mountain well field were ing Forest Highland, Flagstaff Ranch, Flagstaff Meadows expanded from only model layer 2 (lower part of the Coconino at Bellmont, Cameron, Leupp, Tusayan, and Grand Canyon aquifer) to include model layer 3 (Redwall-Muav aquifer). Village. These additional WWTFs were not included in the Well locations at the Woody Mountain well field were moved original NARGFM simulations because either the estimated as much as 1.5 miles laterally to reduce the concentration of incidental recharge rate for each facility was estimated at less pumping in single model cells. Withdrawals from two wells than 50 ac-ft/yr or the facilities did not exist before 2005. at the Lake Mary well field were expanded from only model Other WWTFs within the CPWAC scenario area at Tuba City layer 2 to include model layer 3. Withdrawals from several and Moenkopi were not simulated because effluent from these wells outside of the CPWAC scenario area near Holbrook facilities is discharged to channels that flow over outcrops of were also relocated to maintain withdrawal rates near the area Mesozoic aquifers and confining units that are hydraulically of CPWAC concern; some were moved as much as 1 mile separated from the simulated aquifers and greatly limit any laterally to reduce the concentration of pumping. Withdrawal recharge to the simulated aquifers. distributions at a few wells near Holbrook were expanded Incidental recharge from the WWTFs was assumed to from only model layer 1 to include model layers 2 and 3. As remain as a constant percentage of water demand for each Withdrawal Scenarios 17 53 72 64 165 249 292 120 146 875 137 186 2,112 8,573 2050-2105 13,042 53 72 64 113 137 243 271 100 753 121 186 7,429 1,830 2040-2049 11,370 53 72 72 80 87 108 235 248 632 104 186 6,225 1,533 9,634 2030-2039 80 46 72 80 72 66 88 228 226 510 186 scenarios 1, 2, and 3 2020-2029 5,306 1,307 8,267 Simulated incidental recharge rate 52 46 72 80 68 41 72 220 203 388 186 4,650 1,145 7,224 2010-2019 24 45 72 64 40 35 24 110 959 181 100 186 2006-2009 3,894 5,734 Arizona Regional Groundwater Flow Model (NARGFM). 3 Tuba City. Effluent from these facilties is discharged to stream channels that cross the Chinle Effluent from these facilties is discharged City. Tuba 0 24 62 50 12 49 26 13 64 80 18 50 32 Incidental groundwater recharge rate as a percent of demand served - 2 2 2 2 2 2 2 NA NA NA NA NA NA NA 80 45 213 455 5,028 1,239 rate, 2000-2005 Simulated inci dental recharge 1 South Rim Community served Munds Park Village Kachina Flagstaff Flagstaff Williams Supai Village Forest Highlands Ranch Flagstaff Meadows Flagstaff Cameron Leupp Tusayan Grand Canyon - 1 Total simulated incidental recharge from waste-water treatment facilities Total Projected and simulated incidental recharge rates at waste-water treament facilities in the Coconino Plateau Water Advisory Council Scenario region for three Projected and simulated incidental recharge rates at waste-water treament facilities in the Coconino Plateau Water

Waste-water treatment facility Waste-water Additional waste-water treament facilities in Coconino County were not simulated including Moenkopi and from waste-water effluent was not included in the original NARGFM for these facilities. Incidental recharge and withdrawals during 2000 to 2005 or the most recent rate as a percent of groundwater demand served is calculated for each facility based on NARGFM simulated rates recharge Incidental recharge Plant Facility Plant Plant Plant ment Plant Plant Plant Treatment 1 2 3 Munds Park Waste-Water Treatment Treatment Munds Park Waste-Water Treatment Waste-Water Village Kachina Treatment Rio De Flag Waste-Water Treatment Hill Waste-Water Wildcat Treatment Waste-Water City of Williams Sewer System Village Supai Treat Forest Highlands Waste-Water Treatment Ranch Waste-Water Flagstaff Meadows at Bellmont Flagstaff Plant Treatment Waste-Water Cameron Plant Treatment Leupp Waste-Water Plant Treatment Waste-Water Tusayan Waste-Water Grand Canyon South Rim and Moenkopi Formations, which are assumed an impermeable upper boundary confining bed for the Northern and withdrawals for facilities that were not simulated in the original NARGFM. reported facility discharge Table 2. Table groundwater withdrawal scenarios. are in acre-feet per year] [Values 18 Simulation of Groundwater Withdrawal Scenarios for the Redwall-Muav and Coconino Aquifer Systems of Arizona a result of the modified distribution of withdrawals, no cells of 2006 was in a state of change resulting from previous varia- went dry and no withdrawals were lost from the simulation in tions in groundwater withdrawals and artificial and incidental the area of interest. recharge. While change had occurred during the simulation of conditions during 1910–2005, the beginning and ending groundwater-flow systems were largely similar. Groundwa- ter in the NARGFM area flows from areas of high rates of Simulated Effects of Withdrawal recharge in the high altitude areas of the White Mountains, Scenarios Mogollon Rim, San Francisco Mountain, Defiance Uplift, and Kaibab Plateau toward the primary discharge areas along the The simulated effects of the three groundwater with- major perennial streams including the Colorado, Little Colo- drawal scenarios are superimposed on the effects of previously rado, Verde, and Salt Rivers. Groundwater also discharged to simulated changes to the groundwater-flow system that have other perennial streams including Clear and Chevelon Creeks resulted from variations in groundwater withdrawals and artifi- near the eastern border of Coconino County, Oak and Syca- cial and incidental recharge in the original NARGFM. Effects more Creeks south of Flagstaff, streams and many springs near of the variations include changes in water-levels in wells, the Grand Canyon, and streams at the western extent of the groundwater storage, discharge to streams and springs, and NARGFM. Evapotranspiration of groundwater was minor in ET by plants that use groundwater. Variations in recharge rates comparison to other water-budget components in the CPWAC were also simulated in the published version of NARGFM region. Local cones of depression were established before (Pool and others, 2011). However, past and possible future 2006 in areas of concentrated groundwater withdrawal includ- recharge variations were not simulated for this analysis ing the Woody Mountain and Lake Mary wells fields near because those variations result in much greater change than Flagstaff. the variations in the scenarios. A constant rate of average Simulated groundwater budgets at the end of 2005 docu- annual-recharge, equivalent to the average recharge during ment the effect of simulated changes in the groundwater-flow 1940–2005, was simulated for the scenarios. Eliminating system (table 3). Groundwater was being withdrawn from recharge variations allows the analysis to focus on the effects storage in all simulated groundwater basins in the NARGFM of only past variations in withdrawals and incidental recharge at the end of 2005. Rates of storage loss in basins that are and the scenario variations in withdrawals. partly within the CPWAC area include 85,000 ac-ft/yr in the Simulation of the scenarios were completed for the period Coconino Plateau basin, 54,000 ac-ft/yr in the Little Colorado 2006 through 2105 using 10 time steps within 6 stress peri- River Plateau basin, and 39,000 ac-ft/yr in the Verde Valley ods. Pre-2050 stress periods included the 5-year period 2006 subbasin. The storage loss occurred as a result of the effects of through 2009 followed by periods of decade length during groundwater withdrawals and variations in artificial and inci- 2010 through 2049. Simulation of conditions through 2105 dental recharge before 2006. Storage losses that occurred in result in only a part of the changes that will occur before a new 2005 indicate that losses in groundwater discharge to streams steady-state groundwater-flow system is attained in the future. and springs will occur after 2005 even if no further changes in If no additional simulated changes in groundwater withdrawal withdrawals and recharge occur. These future declines in rates and recharge were too occur after 2105, the groundwater-flow of net discharge to streams and springs in the NARGFM will system would eventually reach a new steady-state condition be less than or equivalent to the simulated rate of storage loss of reduced but constant storage, and reduced discharge to in 2005. Eventually, given no future changes in withdrawals streams, springs, and ET. However, changes that may occur and recharge, a new steady-state groundwater-flow system will after 2105 are not addressed in this analysis. result and all of the rates of loss in storage will be replaced by reduced rates of discharge to streams and springs. Rates of discharge to streams, springs, and ET that were Initial Conditions for the Scenarios simulated during 2005 will likely decrease during the simu- lated future withdrawal scenarios as a result of past withdraw- The groundwater-flow system simulated by a modified als throughout the NARGFM. Reduced streamflow derived version of the NARGFM at the beginning of 2006 represents from groundwater may also result in greater infiltration of initial conditions for simulations of the three withdrawal runoff; however, the NARGFM simulates only groundwa- scenarios (fig. 3). Specifically, the simulated hydraulic heads ter processes. Changes in discharge to streams and springs throughout the model at the end of 2005 are used as the will occur within the groundwater basins that lie nearest to initial hydraulic heads for the scenarios. Modifications to the Coconino County including the Coconino Plateau and Little published NARGFM included simulation of average-annual Colorado River Plateau basins and the Verde Valley subbasin. recharge rates rather than variable recharge rates, and redistri- Simulated groundwater discharge in these basins occurs to bution of withdrawals at the Woody Mountain well field across the Blue Springs and the Lower Little Colorado River, Clear a slightly greater area for the purpose of maintaining saturated Creek, Chevelon Creek, the Colorado River, numerous springs conditions in the uppermost model layer through the scenario above the Colorado River, Havasu Creek, and the Verde River period to 2105. The groundwater-flow system at the beginning and tributary streams including those nearest to the CPWAC Simulated Effects of Withdrawal Scenarios 19 0 500 N/A 1,800 1,600 Verde Verde Canyon 11,400 62,800 61,000 33,100 61,300 76,400 26,400 21,700 -15,200 sub-basin 201,200 0 8,000 1,600 Verde Verde Valley Valley 11,900 38,500 98,400 19,500 25,800 68,600 -39,000 -17,800 sub-basin 116,700 537,700 59,9004 155,600 Verde 0 part of sub-basin gaging stations near 2,010 1,700 9,300 1,600 Verde Valley sub-basin Valley Verde 24,700 62,200 74,000 13,400 46,100 -11,800 -30,200 between the streamflow- Clarkdale and near Camp 295,500 37,6004 104,200 0 0 Clarkdale 200 Verde Valley Valley Verde the streamflow- 8,800 2,600 sub-basin above part of sub-basin -8,800 -6,000 13,800 36,100 22,300 45,100 14,900 53,900 22,500 gaging station near 242,200

0 Chino 2,600 5,100 2,000 sub-basins 11,200 19,900 17,300 28,900 51,800 29,500 80,400 33,000 Verde River Basin groundwater-flow system River Basin groundwater-flow Verde -28,600 Big and Little 24,4003 -469,800

0 1,900 4,200 3,500 1,900 11,200 18,100 16,200 40,800 26,900 58,100 31,200 -17,400 Big Chino sub-basin 116,700 23,4003 0 Area 700 200 sub-basins 1,800 1,100 9,200 1,800 1,000 1,800 3,100 Management 24,200 14,800 28,900 Prescott Active Little Chino and -14,100 Upper Agua Fria -703,600 0 700 100 1,800 1,100 7,000 1,500 2,600 1,800 11,000 17,800 22,200 1,0002 sub-basin -11,200 Little Chino -586,500 N/A N/A N/A 0 sub-basin 100 2,300 1,000 4,600 1,000 7,500 1,000 6,400 1,300 Upper Agua Fria -2,900 -117,100 1j 1f 1i 1k 1a 1b 1c 1d 1e 1g 1h -flow budgets at the end of 2005 for selected regions of the Northern Arizona Regional Groundwater-Flow Model from Pool and others (2011). -flow budgets at the end of 2005 for selected regions Northern Arizona Regional Groundwater-Flow Total Inflow Total Total Outflow Total from base flow predevelopment Net streamflow adjacent basins Natural recharge drains (base flow) Incidental recharge Groundwater withdrawals Simulated groundwater Evapotranspiration by phreatophytes

Net groundwater flow to (-) and from (+) Net rate of groundwater storage change Groundwater outflow to adjacent areas Groundwater inflow from adjacent areas Discharge to streams and springs simulated as Cumulative groundwater storage change since Groundwater discharge to streams (base flow) Recharge from infiltration of streamflow derived Arizona Department of Water Arizona Department of Water Resources basin type Outflow Groundwater Basin Groundwater-budget component Groundwater-budget Inflow Table 3. Table are in acre-feet per year except for cumulative values, which acre-feet. N/A, not applicable] [Values 20 Simulation of Groundwater Withdrawal Scenarios for the Redwall-Muav and Coconino Aquifer Systems of Arizona

- - N/A N/A N/A N/A 0 basins 600 1,200 Black River, and Black River, White River sub- 10,800 10,800 Salt River Canyon, streamflow-gaging -58,400 station at Roosevelt Salt River above the 133,300 145,200 203,200 203,700 1,205,600 200 N/A N/A N/A N/A basin 1,300 1,900 1,300 1,600 Lakes 28,300 31,500 43,200 44,700 Salt River -13,200 326,600 N/A N/A N/A N/A 1,900 1,100 2,700 Tonto Tonto basin Creek 39,700 26,400 67,900 84,100 87,900 23,600 Salt River sub-basins groundwater-flow system Salt River sub-basins groundwater-flow -20,100 322,400 - 1l 1g 100 500 N/A N/A N/A N/A 9,400 -3,600 31,400 40,900 42,000 13,000 55,500 basins Western Western -14,600 ter basin simulated 325,200 groundwa N/A N/A N/A N/A 100 100 sub-basin 3,300 1,700 5,100 2,900 3,300 6,300 -1,600 -1,200 and Wikieup 37,900 Springs basin Truxton Wash Truxton Parts of Peach 0 0 N/A N/A N/A N/A 1,500 9,700 (Trout (Trout Creek) -8,200 -6,900 14,600 16,100 13,300 23,100 Fort Rock sub-basin 156,700 Western basins groundwater-flow system basins groundwater-flow Western 0 0 400 N/A N/A N/A occur for any basin. to streams. Both components are simulated using the Streams Package (STR). charge watershed. Wash Truxton sub-basin within the Wikieup parts of the Peach Springs Basin and Agua Fria sub-basins. tions of the Big Chino (about 1,000 ac-ft per yr) and Upper from the Little Chino sub-basin. 6,200 6,200 Burro Creek -6,500 13,400 19,700 25,800 26,100 sub-basin 130,600 N/A Multiple areas of groundwater inflow and outflow may Outflow. Total Inlow minus Total 1i- Calculated as 1j- Calculated as Groundwater Infow minus Outflow. from infiltration of streamflow derived base flow minus Groundwater dis 1k- Calculated as Recharge 1l- Includes the sum of groundwater budget components for Burro Creek and Fort Rock sub-basins 2- Includes groundwater outflow of about 2,100 ac-ft per yr to the Big Chino sub-basin and inflow from por 3- Includes the balance of outflow groundwater to adjacent basins and inflow from basins, primarily 4- Does not include diversion of 34,600 acre-ft per year base flow that is transpired by crops. - 0 0 N/A N/A N/A N/A areas 9,000 north of the 75,200 38,100 29,100 and adjacent -31,800 several basins Kanab Plateau 113,300 Colorado River 135,900 145,000 1,021,000 ge of groundwater to streams ge of groundwater to streams N/A N/A N/A N/A 0 0 600 Peach Springs 5,100 5,400 7,600 4,900 Wash watershed Wash -1,900 outside of Truxton outside of Truxton 10,500 12,400 70,800 Part of basin that lies 300 500 800 N/A basin Plateau Coconino 25,100 -54,000 113,900 190,400 305,100 173,000 160,700 359,500 165,300 172,700 1,275,100 Colorado River Basin groundwater-flow system Colorado River Basin groundwater-flow - 0 0 rado 300 basin 2,600 Little Colo 13,100 49,800 13,100 81,700 -85,000 154,900 220,300 210,400 305,600 669,500 -207,900 1j 1f 1i 1k 1a 1b 1c 1d 1e 1g 1h flow) Total Inflow Total Total Outflow Total

Net streamflow adjacent basins Natural recharge Incidental recharge as drains (base flow) since predevelopment derived from base flow Groundwater withdrawals Simulated groundwater-flow budgets at the end of 2005 for selected regions of the Northern Arizona Regional Groundwater-Flow Model from Pool and others (2011). budgets at the end of 2005 for selected regions Northern Arizona Regional Groundwater-Flow Simulated groundwater-flow

Evapotranspiration by phreatophytes Recharge from infiltration of streamflow Net groundwater flow to (-) and from (+) Net rate of groundwater storage change Groundwater outflow to adjacent areas Cumulative groundwater storage change Groundwater discharge to streams (base Groundwater inflow from adjacent areas (simulated using the MODFLOW Streams Package (STR)) within the groundwater basin and in upgradient groundwa (simulated using the MODFLOW ter basins. from waste-water treatment facilites, and golf courses. discharge to streams in the groundwater basin. of groundwater discharge recharge and in the Little Colorado River Basin. Verde Discharge to streams and springs simulated Groundwater Basin Arizona Department of Water Resources basin type component Groundwater-budget Inflow Outflow 1a-Includes the total of simulated streamflow infiltration; all which is derived from dischar resulting from excess applied irrigation water derived surface and groundwater supplies, 1b-Includes recharge 1c- Includes components of groundwater inflow from multiple adjacent basins and sub-basins. 1d-Represents the sum of inflow components including groundwater flow from adjacent basins and reinfiltration Streams Package (STR). to streams simulated using the MODFLOW 1e-Includes only discharge Drain Package (DRN). 1f- Streams and springs simulated using the MODFLOW River Basin above the streamflow-gaging station near Camp Verde 1g- Evapotranspiration was simulated in only the 1h- Includes components of groundwater outflow to multiple adjacent basins and sub-basins. Table 3. Table —Continued. Simulated Effects of Withdrawal Scenarios 21 region, Sycamore Creek, Oak Creek, Beaver Creek, and West imported surface water to the Flagstaff and Williams areas and Clear Creek. Discharge to streams in the Little Colorado River associated reduced groundwater withdrawals for scenario 3. Plateau basin—13,100 ac-ft/yr in 2005—primarily occurs along Clear, Chevelon, and Silver Creeks and along the upper Scenario 1 reaches of the Little Colorado River. The discharge also infiltrates and recharges in downstream reaches of the stream Simulated water-level change is dominated by declines network. As a result, both discharge and recharge along the of 1 to 5 ft across most of the CPWAC and adjacent areas streams in the Little Colorado River Plateau basin will change for scenario 1 during 2006–2105 (fig. 5). Most of the larger at equivalent rates during scenario simulations. changes occur in areas near major withdrawal wells and areas of incidental recharge at major wastewater treatment plants and facilities. In 2105, the simulation predicts water-level declines Scenario Simulation Results of more than 100 ft near the Woody Mountain and Lake Mary well fields and the towns of Tusayan and Parks. Maximum Scenarios 1, 2, and 3 each result in a different set of sim- declines near Williams and Moenkopi are about 50 ft. Declines ulated hydrologic changes within the modeled area. Change of 10 to 50 ft are simulated near other major withdrawal wells simulated by scenario 1 represents change that will occur near Sedona, Munds Park, Winona, Leupp, and Red Gap due to projected increased demand for groundwater without Ranch. Water-level rises of more than 100 ft are simulated near management decisions to limit groundwater withdrawals, the City of Flagstaff Waste-Water Treatment Plants at Wildcat using water imported to the area through a proposed pipeline. Hill, Rio De Flag, and Grand Canyon Village. Water-level Change simulated by scenarios 2 and 3 represents change rises of 1 to 10 ft simulated near Clear and Chevelon Creeks resulting from the proposed pipeline and less groundwater result from pre-2006 changes in withdrawals or incidental withdrawals than simulated by scenario 1. Scenario 2 includes recharge outside of the scenario area that were continued into a limited extent of the pipeline to the Cameron area. Scenario the scenario period. Apparent water-level recovery resulted in 3 represents the greatest pipeline extent, maximum importa- resaturation of model cells during the scenario simulation in tion of water to the greatest area, and the least amount of several areas including south of Williams, northwest of Tuba simulated groundwater withdrawals. For this analysis of future City, small areas near Clear and Chevelon Creeks, and small water use scenarios developed by the CPWAC, comparisons of areas in Verde Valley. Most of the resaturated areas are at the hydrologic changes resulting from the scenarios are made for margins of model layers where the layer is thinnest and suscep- only the region in and near the CPWAC scenario area. Differ- tible to dewatering. Resaturation is caused by changes in well ences in simulated water-level change in the primary aquifers withdrawals and incidental recharge in the scenario relative to are compared for conditions simulated at the end of 2105 for the original NARGFM at the end of 2005. each scenario. Simulated changes in groundwater discharge to major perennial streams and springs resulting from each Scenarios 2 and 3 scenario are also discussed. The major streams and springs include Havasu Creek, the Colorado River, four simulated Importing water and eliminating major withdrawal wells springs on the south rim of Grand Canyon, the lower reach after 2009 in the Cameron area resulted in less water-level of the Little Colorado River below Cameron including Blue decline and slightly higher water levels in scenario 2 compared Springs, Chevelon Creek, Clear Creek, Oak Creek, and the to scenario 1 from 2006 to 2105 (fig. A6 ). Less water-level upper Verde River above the streamflow gaging station near decline was simulated and water levels for Scenario 2 were Clarkdale. slightly higher than in Scenario 1 across nearly all of the sce- nario region. In the Cameron areas area, scenario 2 water levels were 1 to 5 ft higher than in scenario 1. Near Moenkopi, a Simulated Changes in Water Levels small area of water levels are as much as 10 ft higher due to the elimination of a proposed withdrawal well that was simulated Simulated water-level change during 2006–2105 in the in scenario 1. CPWAC region is discussed for scenarios 1, 2, and 3. Scenario The effects of importing water beyond the Cameron area 1 water-level declines are the greatest of the three scenarios to Flagstaff and Williams and reducing groundwater withdraw- because it includes the assumption that no water would be als in the area during 2006 to 2105 are shown on a map of the imported to the region and groundwater withdrawals would difference in water-level change simulated by scenario 3 in continue to supply a large portion of the water demand for the comparison to scenario 1 (fig. B6 ). Results near Cameron and area. As a result, scenario 1 includes the greatest increase in Moenkopi are similar to scenario 2 because well withdrawals groundwater withdrawals. Scenario 1 water-level changes are in those areas were similar for both scenarios 2 and 3 and less treated as a baseline for comparison with water-level change than in scenario 1. Water levels for scenario 3 are about 1 to resulting from scenarios 2 and 3, which include imported sur- 5 ft higher in comparison to scenario 1 across about one-half face water and reduced groundwater withdrawals in the Cam- of the Coconino Plateau between Williams and the Colorado eron and Moenkopi areas for scenario 2, and extension of the River. Water levels simulated near withdrawal wells in the 22 Simulation of Groundwater Withdrawal Scenarios for the Redwall-Muav and Coconino Aquifer Systems of Arizona

113° 112° 111°

0 5 10 20 30 40 MILES

37° 0 10 20 40 60 80 KILOMETERS

Page

Kaibab

River Havasu Layer Plateau Blue Springs Cr resaturation Colorado eek Complex Supai Tuba City Black Moenkopi Mesa Grand Canyon 36° Village Coconino Tusayan Little Colorado Cameron Plateau River Plateau basin basin

Valle Little Peach Colorado Springs Flagstaff sub-basin Local Red Lake well field San Francisco River Mountain Leupp Fort Rock Williams Red Gap sub-basin Big Chino Flagstaff Winona Ranch Parks well field sub-basin Layer Woody rout Mountain T resaturation Lake Mary Winslow 35° eek well field Munds well field Cr Verde V alley Park Verde Riversub-basin Mogollon Rim eek Cr eek eek Sedona Cr Cr eek Clear Cr o Oak Layer Burr Creek resaturation Little Beaver

Chino Prescott Clear Creek Chevelon West sub-basin

County boundaries of the United States, USGS 2000 National Atlas, 1:2,000,000-scale resolution, 2002, USGS; Perennial streams from Arizona Department of Water Quality, 2015, Towns from USGS Geographic Names Information System, 1981. Coordinate System: NAD 1927. UTM Zone 12N. scale 1:100,000 Projection: Transverse Mercator. Datum: North American 1927. False Easting: 500,000.0000. False Northing: 0.0000. Central Meridian: -111.0000. Scale Factor: 0.9996. Latitude Of Origin: 0.0000. Units: Meter.

EXPLANATION Town or landmark Model layer 1 active extent Perennial streams Model layer 2 active extent Simulated stream Model layer 3 active extent Groundwater basin and subbasin boundary Simulated water-level change Coconino County boundary Feet

0 0 0 0 -5 -1 1 5 0 0 0 0 0 0 -5 1 – – 1 5 0 0 <1 -1 - – – 0 1 – – 1 >1 – – -1 0 5 10 0– 0– 10 -5 5 -5 - Figure 5. Map of water-level change for scenario 1 in the uppermost model layer from 2006 through 2105 near the Coconino Plateau Water Advisory Council scenario region and surrounding areas, Arizona. ADWR, Arizona Department of Water Resources. Simulated Effects of Withdrawal Scenarios 23

A 113° 112° 111°

0 5 10 20 30 40 MILES 37°

010 20 40 60 80 KILOMETERS

River Havasu Kaibab Creek Plateau Colorado Blue Springs Supai Complex Tuba City Black Mesa Moenkopi 36° Grand Canyon Village Tusayan Coconino Little Colorado Plateau Cameron River Plateau basin basin

Valle Little Peach

Springs Colorado Flagstaff sub-basin Local well field Red Lake San Francisco River X Mountain Fort Rock Leupp Williams sub-basin Big Chino Parks Winona Red Gap sub-basin Flagstaff Ranch Woody well field Mountain Trout Lake Mary well field Winslow 35° Creek well field Verde Valley Verde River Munds Mogollon Rim Park Creek Sedona Creek Creek Clear Creek ro Oak sub-basin Creek Bur Little Beaver Creek Chino Clear Chevelon Prescott West sub-basin

County boundaries of the United States, USGS 2000 National Atlas, 1:2,000,000-scale resolution, 2002, USGS; Perennial streams from Arizona Department of Water Quality, 2015, Towns from USGS Geographic Names Information System, 1981. Coordinate System: NAD 1927 UTM Zone 12N. scale 1:100,000; Groundwater basin and sub-basin boundaries from Projection: Transverse Mercator. Datum: North American 1927. False Easting: 500,000.0000. False Northing: 0.0000. Arizona Department of Water Resources, 2008, scale 1:100,000 Central Meridian: -111.0000. Scale Factor: 0.9996. Latitude Of Origin: 0.0000. Units: Meter

EXPLANATION

Town or landmark Model layer 1 active extent Perennial streams Model layer 2 active extent Simulated stream Model layer 3 active extent Coconino County boundary Simulated difference in water levels in Scenario 2 relative to Scenario 1 Groundwater basin and subbasin boundary Feet

0 - 1 1 - 5 <-100 -1 - 0 5 - 10 >100 -10 - -5 -5 - -1 10 - 50 -50 --10 50 - 100 -100 --50 Figure 6. Map of the difference in water-level change in the uppermost model layer compared with scenario 1 from 2006 to 2105 near the Coconino Plateau Water Advisory Council Scenario region and surrounding areas, Arizona for (A) Scenario 2 and (B) Scenario 3. 24 Simulation of Groundwater Withdrawal Scenarios for the Redwall-Muav and Coconino Aquifer Systems of Arizona

B 113° 112° 111°

0 5 10 20 30 40 MILES 37°

010 20 40 60 80 KILOMETERS

River Havasu Kaibab Creek Colorado Plateau Blue Springs Black Complex Supai Mesa Tuba City

Moenkopi 36° Grand Canyon Village Coconino Little Colorado Plateau Tusayan River Plateau basin Cameron basin

Little Valle Peach

Springs Colorado sub-basin Flagstaff Local well field Red Lake San Francisco Fort Rock X Mountain River sub-basin Parks Big Chino Williams Winona Leupp sub-basin Red Gap Flagstaff Ranch Woody well field rout T Mountain Verde Valley Winslow 35° Creek well field Lake Mary sub-basin well field Mogollon Rim River Verde Munds Park Creek Sedona Creek Creek Clear Creek ro Oak

Bur Creek Little Beaver Creek Chino Clear Chevelon West sub-basin Prescott

County boundaries of the United States, USGS 2000 National Atlas, 1:2,000,000-scale resolution, 2002, USGS; Perennial streams from Arizona Department of Water Quality, 2015, Towns from USGS Geographic Names Information System, 1981. Coordinate System: NAD 1927 UTM Zone 12N. scale 1:100,000; Groundwater basin and sub-basin boundaries from Projection: Transverse Mercator. Datum: North American 1927. False Easting: 500,000.0000. False Northing: 0.0000. Arizona Department of Water Resources, 2008, scale 1:100,000 Central Meridian: -111.0000. Scale Factor: 0.9996. Latitude Of Origin: 0.0000. Units: Meter

EXPLANATION Town or landmark Model layer 1 active extent Perennial streams Model layer 2 active extent Simulated stream Model layer 3 active extent Coconino County boundary Simulated difference in water levels in Scenario 3 relative to Scenario 1 Groundwater basin and subbasin boundary Feet

0 - 1 1 - 5 <-100 -1 - 0 5 - 10 >100 -10 - -5 -5 - -1 10 - 50 -50 --10 50 - 100 -100 --50 Figure 6.—Continued Simulated Effects of Withdrawal Scenarios 25 vicinity of Williams and Flagstaff are 10 to 50 ft higher than Clear Creek, Chevelon Creek, Silver Creek, Oak Creek, Syca- simulated by scenario 1. more Creek, Beaver Creek, and West Clear Creek. Simulated major springs in the CPWAC region include Havasu Spring, Blue Springs, and five of the major springs on the south rim Simulated Changes in Groundwater Discharge of Grand Canyon—Royal Arch, Hermit, Monument, Indian Simulated changes in groundwater discharge to streams Gardens, and Grapevine Springs. Groundwater discharge to all and springs are discussed for each scenario. Groundwater of these features can be captured by groundwater withdrawals discharge to streams, springs, and vegetation will decrease or enhanced by artificial or incidental recharge. Groundwater as a result of well withdrawals and increase with incidental discharge to other surface water features that are hydrauli- recharge (Winter and others, 1998; fig. 7). Initial well with- cally connected to the Coconino and Redwall-Muav aquifers drawals are derived from aquifer storage within the cone of but not simulated may also change. These features that were depression around the well, which also creates local ground- not simulated, however, have less groundwater discharge than water gradients that direct groundwater flow to the well the simulated features. Simulation of changes in discharge to (Barlow and Leake, 2012). The cone of depression is an area these features would require a more detailed groundwater flow of decreased fluid pressure around the well, with the greatest model. decrease in fluid pressure at the well. As withdrawals from the Simulated changes in discharge occur at each of the well continue, the area of reduced fluid pressure expands and major groundwater discharge features for all three scenarios, ultimately reaches any areas where groundwater discharges to but most of the change before 2105 is very small (fig. 8). The surface features. Withdrawals later in time are derived from greatest simulated changes in groundwater discharge occur a combination of aquifer storage and decreased discharge to with scenario 1. The most change is simulated for the Little surface water features. The effect of incidental recharge is the Colorado River below Cameron (fig. D8 ) and for Oak Creek opposite of well withdrawals, with water first going into stor- above Page Springs (fig. 8G) where declines in discharge of about 1.3 and 1.1 cubic feet per second (ft3/s) occur, respec- age and increasing discharge to surface features with time. tively. Other simulated changes in discharge through 2105 are Simulated distributions of changes in groundwater losses of less than 0.4 ft3/s at the Upper Verde River (fig. 8H), discharge result from three factors including (1) the distance losses of less than 0.3 ft3/s at Havasu Creek (fig. 8A) and at of each discharge feature to groundwater withdrawal wells or Colorado River below Havasu Creek (fig. B8 ), losses of less incidental recharge, (2) aquifer transmissivity, and (3) aquifer- than 0.1 ft3/s at Clear Creek, and increases in flow at the south storage properties. The rate of discharge change decreases rim springs (fig. 8B) and Chevelon Creek (fig. F8 ) of less than with distance between the withdrawal or recharge and the 0.1 and 0.3 ft3/s, respectively. Simulated changes in discharge discharge feature. The rate of discharge change increases with for scenarios 2 and 3 are less because of lower rates of ground- higher aquifer transmissivity and with lower aquifer-storage water withdrawal with respect to scenario 1. properties. Rates of discharge change will be greatest for a discharge feature that is hydraulically connected to a highly transmissive confined aquifer. Scenario 1 The NARGFM simulates groundwater discharge to Reductions in groundwater discharge occur at most of the streams, springs, and vegetation. This analysis focuses, how- major perennial streams and springs near the CPWAC area for ever, on changes in discharge to streams and springs, which scenario 1. However, increases in discharge, both short-term generally occur before changes in vegetation use. Eventually, and long-term, occur at some perennial features. The changes given enough time with no further changes in well withdraw- at each major discharge feature are discussed including expla- als and recharge rates, all of the well withdrawals will be nations of the simulated change. derived from decreased groundwater discharge to surface The location of the greatest simulated losses in ground- features, no further change in aquifer storage will occur, and a water discharge along the Little Colorado River below new steady-state groundwater-flow system will be established. Cameron result from several causes, including groundwater For this analysis, the effects of withdrawals for each scenario withdrawals from the Coconino aquifer in the Cameron and are analyzed for the period before 2105, which is long before a Moenkopi areas, relatively high transmissivity values in the new steady-state flow system will be established. Any changes region, and confined aquifer conditions east of Cameron in storage that are simulated in 2105 will eventually, at some including at a proposed well at Moenkopi. Losses in ground- future time, result in an equivalent reduction in groundwater water discharge to Oak Creek for scenario 1 are primarily discharge to streams and springs. the result of nearby large groundwater withdrawals at sev- Simulated changes in groundwater discharge to streams eral wells including those at the Woody Mountain and Lake and springs from 2006 to 2105 are discussed for major simu- Mary well fields. The initial simulated increase in flow in lated perennial streams and springs that lie within and near- Oak Creek, about 0.1 ft3/s before about 2010, is likely caused est to the CPWAC scenario region. These simulated features by the addition of incidental recharge at the nearby Kachina include the major perennial rivers—Colorado, Little Colorado, Village and Munds Park Wastewater Treatment facilities to and Verde—and tributary streams including Havasu Creek, the simulation. These incidental recharge features were not 26 Simulation of Groundwater Withdrawal Scenarios for the Redwall-Muav and Coconino Aquifer Systems of Arizona

1.0 Figure 7. Graph of sources of water, storage 0.9 Decrease in surface-water flow or surface-water flow and 0.8 plus decrease in evapotranspiration evapotranspiration, to a pumped well through time. 0.7

0.6

0.5 0.4 0.3 Fraction of well pumping rate 0.2 Decrease in storage 0.1

0.0 Increasing time simulated in the original NARGFM and are a new source of that were included in all three scenarios, but were not included simulated recharge beginning in 2006 for all three scenarios. in the original NARGFM. The combined increase in flow of The maximum decline in flow in Oak Creek of about 1.1 ft3/s the south rim springs (Royal Arch, Hermit, Monument, Indian by 2105 is less than 5 percent of the base flow of Oak Creek Gardens, and Grapevine) reaches a simulated maximum of and well within the typical streamflow measurement error. about 0.1 ft3/s in about the year 2050. From this point on, the Lesser rates of groundwater discharge decline are simu- simulated change in flow for the combined south rim springs lated at Havasu Creek (fig. A8 ), the Colorado River below declines to about 0.05 ft3/s at year 2105. Havasu Creek (fig. 8B), and Upper Verde River (fig. 8H). Increased simulated discharge along Chevelon Creek Simulated declines in flow at Havasu Creek before 2040 are through the simulated period results from pre-2006 changes in primarily caused by nearby supply wells for the Havasupai groundwater withdrawals and incidental recharge outside of Tribe. The longer term decline in discharge of less than the CPWAC area. These pre-2006 changes in stresses also are 0.3 ft3/s in 2105, however, is likely caused by distant and the cause of the simulated water-level recovery in the Chev- regional groundwater withdrawals from the aquifer. The simu- elon Creek area and areas to the east (fig. 5). The simulated lated rate of decline for Havasu Creek compared to the present flow increase of about 0.3 ft3/s by about 2105 represents about day base flow of Havasu Creek (61 ft3/s) would be impercep- an 11 percent increase in the current base flow of Chevelon tible. Simulated trends in declining groundwater discharge to Creek below the dam. Clear Creek (fig. E8 ) displays a small the Colorado River below Havasu Creek are similar to those increase in discharge before about 2030, which is caused by at Havasu Creek and have the same causes, but are slightly the same changes in pre-2006 stress that caused the greater less in magnitude. Declines in groundwater discharge of less and longer-term change in Chevelon Creek discharge. The than 0.4 ft3/s to the upper Verde River above the streamflow increase in discharge at Clear Creek is reversed by the effects gaging station near Clarkdale are likely a result of both the of nearby groundwater withdrawals after about 2030. This delayed effects of pre-2006 changes in nearby groundwater represents less than about 2 percent of the estimated summer withdrawals, and post-2005 scenario 1 changes in distant base flow of Clear Creek (Leake and others, 2005). groundwater withdrawals near Williams. The Redwall-Muav aquifer is simulated as highly transmissive in the region north Scenarios 2 and 3 of the Verde River; as a result distant well withdrawals may Simulated groundwater discharge for scenarios 2 and 3 capture some groundwater discharge to the Verde River above reflect the decrease in groundwater withdrawals resulting from the streamflow gaging station near Clarkdale. For comparison, importing surface water. Simulated discharge at major peren- the current base flow of the Verde River at Clarkdale is about nial streams and springs for scenarios 2 and 3 was greater than 69 ft3/s. Long-term increases in simulated groundwater discharge scenario 1 at many of the simulated groundwater discharge (decades or longer duration), occurred for scenario 1 along features (fig. 8). Scenarios 2 and 3 had no influence on simu- several of the major perennial streams and springs, includ- lated groundwater discharge at Clear and Chevelon Creeks ing springs at the south rim of Grand Canyon (fig. B8 ), along from 2006 through 2105 (figs. 8E,F) because the reduced Chevelon Creek (fig. F8 ), and along Clear Creek (fig. E8 ). The groundwater withdrawals are distant from those features and increased discharge at the south rim springs is likely caused by any effects may occur later. incidental recharge of treated effluent at the wastewater treat- Scenario 2, reduced groundwater withdrawals in the ment plants at Grand Canyon and Tusayan, which are features Cameron area, produces results similar to scenario 1 for all Simulated Effects of Withdrawal Scenarios 27

0.1 0.1 Figure 8. Simulated A Havasu Creek B Colorado River below Havasu Creek changes in groundwater 0.0 0.0 discharge to major -0.1 -0.1 perennial surface -0.2 -0.2 water features from -0.3 -0.3 2006 through 2105 in

-0.4 -0.4 and near the Coconino Plateau Water Advisory -0.5 -0.5 Council scenario region: 0.5 0.5 C South Rim Springs D Little Colorado River below Cameron (A) Havasu Creek, (B) 0.4 Colorado River below 0.0 0.3 Havasu Creek, (C) major

0.2 -0.5 springs at the south rim of Grand Canyon, (D) 0.1 -1.0 Little Colorado River 0.0 below Cameron, (E) -0.1 -1.5 Clear Creek, (F) Chevelon 0.1 0.5 Creek, (G) Oak Creek E Clear Creek F Chevelon Creek 0.0 0.4 above Page Springs, and (H) upper part of the -0.1 0.3 Verde River between 0.2 -0.2 the streamflow gaging Change in flow, cubic feet per second Change -0.3 0.1 stations near Paulden -0.4 0.0 and near Clarkdale.

-0.5 -0.1 0.5 0.1 G Oak Creek above Page Springs H Upper Verde River 0.0 0.0 -0.1 EXPLANATION -0.5 -0.2 -0.3 Scenario 1 -1.0 Scenario 2 -0.4 Scenario 3 -1.5 -0.5 2000 2010 2020 2030 2040 2050 2060 2070 2080 2090 2100 2110 2000 2010 2020 2030 2040 2050 2060 2070 2080 2090 2100 2110

major groundwater discharge features except for the peren- River below Havasu Creek was greater than that simulated nial reach of the Little Colorado River below Cameron, which by scenarios 1 and 2 by about 0.5 ft3/s. Scenario 3 simulated is nearest to the reduced withdrawal area. Scenario 2 results groundwater discharge through 2105 at Oak Creek above Page in about 0.1 ft3/s loss in simulated discharge through 2105 in Springs and the upper Verde River was greater than simulated comparison to discharge simulated in 2005, whereas scenario by scenarios 1 and 2 by about 0.05 ft3/s. Increases in discharge 1 resulted in a loss in discharge of about 1.3 ft3/s . to Oak Creek and the upper Verde River are likely because of Scenario 3 had a broader effect on groundwater dis- reduced simulated groundwater withdrawals near Flagstaff and charge across the region because of a greater extent of reduced Williams, respectively. Slightly greater groundwater discharge, groundwater withdrawals. Scenario 3 resulted in greater about 0.02 ft3/s, was simulated by scenario 3 in comparison groundwater discharge than scenarios 1 and 2 at all major with scenario 1 and 2 at the south rim springs. groundwater discharge features from 2006 through 2105 except for Clear and Chevelon Creeks. The effect on discharge to the Little Colorado River below Cameron was small with Model Limitations respect to scenario 2— about 0.05 ft3/s more discharge was The accuracy of hydrologic change that results from the simulated in 2105—resulting in little change in discharge rate simulation of the CPWAC withdrawal scenarios is dependent since 2006. Greater groundwater discharge was simulated on the persistence of hydrologic assumptions that are inher- by scenario 3 in comparison to scenarios 1 and 2 at Havasu ent in the NARGFM. Major assumptions include, but are not Creek, Colorado River below Havasu Creek, Oak Creek limited to, the reasonably accurate simulation of (1) transmis- above Page Springs, and upper Verde River. In 2105, scenario sivity distributions, (2) distributions of hydraulic properties 3 simulated discharge at Havasu Creek and the Colorado 28 Simulation of Groundwater Withdrawal Scenarios for the Redwall-Muav and Coconino Aquifer Systems of Arizona that control interactions between vertically adjacent aquifers, adjacent states. The model includes the region of the Colorado (3) distributions of spatial, including vertical, withdrawal Plateau and adjacent areas to the south that include alluvial and incidental recharge rates, (4) aquifer extents, and (5) basins. Three model layers are used to simulate the primary hydrologic barriers and conduits. In addition, no variations hydrogeologic units across the model domain. Within and in recharge rates were simulated for the scenarios and no surrounding the area of the CPWAC withdrawal scenarios, the attempts were made to predict future recharge rates. Recharge major simulated aquifers are the Coconino and Redwall-Muav rates were simulated as equivalent to average annual rates aquifers. The upper part of the Coconino aquifer, included simulated for the original NARGFM. Future studies may within model layer 1, is primarily in the region north and east result in an improved understanding of the groundwater-flow of the Little Colorado River. The lower part of the Coconino system that could substantially alter the conceptual hydrogeo- aquifer, included within model layer 2, is simulated where the logic model in some areas. Commensurate modifications to upper and middle Supai Formations are regionally saturated in the numerical model would be required, resulting in improved the region east of a line from Cameron to Williams. Alluvial simulation of aquifer and stream-aquifer interactions and more aquifers are simulated in the adjacent Verde Valley and include reliable estimates of the effects of future groundwater use and the fluvio-lacustrine facies of the Verde Formation, which are management practices. simulated within model layer 1, and the sand and gravel facies The accuracy of the simulated scenarios is limited to of the Verde Formation, which are simulated as model layer basin-scale applications and to regions of the model where 2. The Redwall-Muav aquifer is simulated as model layer geologic and hydrologic data are available, including records 3 throughout most of the region of the CPWAC withdrawal of steady-state water levels and base flow, and transient scenarios. changes in water levels, base flow, and withdrawals. Basin- The NARGFM simulates aquifer recharge and discharge scale applications refer to the simulation of overall water to streams and springs, and evapotranspiration by phreato- budgets and groundwater flow in a groundwater basin or phytes. Recharge rates and distributions are derived from a large part of the basin. Few hydrologic records that document basin characterization model that estimates recharge as direct withdrawals and major changes in the hydrologic system are infiltration. The recharge estimates are modified in alluvial available across some regions of the groundwater flow system basins to include infiltration along ephemeral stream chan- that are affected by the CPWAC withdrawal scenarios. The nels. Discharge to streams and springs are simulated using the most prominent areas lacking hydrologic data include much MODFLOW stream package for perennial streams within the of the Coconino Plateau basin, parts of the Little Colorado Verde and Little Colorado River drainage systems, and the River Plateau basin, and the Verde Valley subbasin. Future MODFLOW drain package for other perennial streams and data collection in these areas, especially the Coconino Plateau major springs including the Colorado and Salt Rivers. basin, may alter the current understanding and simulation of Three future groundwater withdrawal scenarios, devel- the groundwater flow system in those areas. Accordingly, the oped by the CPWAC for tribal and nontribal uses, were simu- hydrologic system simulated by the NARGFM should not be lated for the period 2006–2105. Most of the withdrawal wells considered a simulation of the true system, but a simulation of for each scenario are within the Coconino Plateau basin and the system as currently understood and simplified for simula- the Little Colorado River Plateau basin. Scenario 1 assumes tion by using a numerical model. However, the ultimate hydro- no major changes in groundwater use except for increased logic effect of any groundwater withdrawal scenario is limited demand based on population projections. Total groundwater by the magnitude of the net withdrawals. withdrawals within the CPWAC region for scenario 1 increase from about 10,800 ac-ft/yr during 2006 through 2009 to about 25,300 ac-ft/yr after 2049 (fig. A3 , appendix 1). Scenario 2 assumes that a pipeline will provide a source of surface water Summary from Lake Powell to the communities along the west edge of the Navajo Reservation including Cameron and Moenkopi, The NARGFM was used to estimate the hydrologic and all nontribal water demands will continue to be met by changes—including changes in water levels and groundwa- groundwater development. Total groundwater withdrawals ter discharge to streams and springs—that may result from within the CPWAC region for scenario 2 increase from about future groundwater withdrawals in and near the CPWAC 10,800 ac-ft/yr during 2006 through 2009 to about study area in Coconino and Navajo Counties, Arizona. Three 23,000 ac-ft/yr after 2049. Most of increases in groundwater future withdrawal scenarios developed by the CPWAC for the withdrawals for scenarios 1 and 2 result from increases for 2006 through 2050 period were tested. Simulated water levels the City of Flagstaff at the Inner City well field and at nearby resulting from each scenario in 2105 were compared, as were communities. Scenario 3 assumes that a pipeline extends onto simulated changes in groundwater discharge to major peren- the Coconino Plateau to supply projected unmet demands for nial streams and springs. water in this area by 2050. Total groundwater withdrawals for The NARGFM uses the USGS developed finite-differ- scenario 3 are the least of the three scenarios, and increase ence code MODFLOW-2005 to simulate groundwater flow from about 10,800 ac-ft/yr during 2006 through 2009 to about within the major aquifers of northern Arizona and parts of 23,400 ac-ft/yr after 2049. Similar to scenarios 1 and 2, most Summary 29 of increases in groundwater withdrawals for scenario 3 result the Coconino Plateau where water-levels declined by 1–5 ft from increases near Flagstaff. Overall groundwater withdraw- by 2105 and local areas with water-level declines of 100 ft or als for scenario 3 after 2049 are about 4,300 ac-ft/yr less than more where groundwater withdrawals are concentrated near those in scenario 1. the City of Flagstaff Woody Mountain and Lake Mary well A few additional assumptions were applied to the with- fields, and the towns of Tusayan and Parks. Water-level rises drawal scenarios regarding rates of natural and incidental of more than 100 ft are simulated near the City of Flagstaff recharge, rates of projected withdrawals outside of the area waste-water treatment plants at Wildcat Hill, Rio De Flag, and of the scenarios, withdrawal rates for exempt wells, and how Grand Canyon Village. to handle loss of withdrawals that occur as a result of model Simulated water-level change from 2006 through 2105 cells that dry during the simulations. Natural recharge rates for scenarios 2 and 3, which bring imported surface water to for the three simulated groundwater withdrawal scenarios are the area and remove some groundwater withdrawals, is mostly assumed to be equivalent to average-annual rates of natural different from water-level change at the local level simulated recharge that applied to the NARGFM for the simulation for scenario 1, which includes no imported water to relieve of pre-2006 conditions. This eliminates the effects of natu- groundwater withdrawals. Scenarios 2 and 3 both eliminate ral recharge from the simulated changes and simplifies the groundwater withdrawals in the reservation areas extending analysis. Projected rates of incidental recharge for waste water from Lake Powell to, and including, Cameron, where water treatment facilities at 12 communities within the CPAC sce- levels in 2105 were 1 to 5 ft higher than simulated for scenario nario region were assumed to remain at a constant percentage 1. Water levels at Moenkopi are more than 10 ft higher due to of water demand from 2000 through 2005. Projected rates of the elimination of a proposed withdrawal well that was simu- incidental recharge at eight golf courses was constant through- lated in scenario 1. Scenario 3 eliminates more groundwater out the simulations. Well withdrawals outside of the CPWAC withdrawals in the Flagstaff and Williams areas; it also simu- scenario area were maintained at rates that were simulated in lates 1 to 5 ft less water-level decline than scenario 1 across the NARGFM during 2000 through 2005. Drying of model much of the Coconino Plateau, and 10 to 50 ft higher water cells that include well withdrawals outside of the scenario area levels than simulated by scenario 1 near withdrawal wells in was allowed to occur. Dry models cells and loss of simulated the Williams and Flagstaff areas. withdrawals at those cells were nearly identical for each Simulated changes in discharge occur at each of the scenario and did not greatly affect results. Withdrawals from major groundwater discharge features for all three scenarios, exempt wells and a few other wells were assumed to vary in but most of the change before 2105 is very small. Scenario 1, the future based on variations in the “other” withdrawal cat- which includes no imported surface water to replace ground- egory provided by each scenario. Distributions of withdrawals water withdrawals, simulated the most change in groundwater for some wells within the scenario area, mainly near the City discharge for the Little Colorado River below Cameron and of Flagstaff wells fields and near Holbrook, were modified for Oak Creek above Page Springs, where discharge declines from the pre-2006 simulation for the purpose of preventing about 1.3 and 1.1 ft3/s , respectively. Other simulated changes drying of the pumped model cell and retention of the projected in discharge through 2105 in scenario 1 are losses of less than withdrawals throughout the period of the simulation. Modifi- 0.4 ft3/s at the upper Verde River, losses of less than 0.3 ft3/s cations included redistribution of the withdrawals to include at Havasu Creek and at the Colorado River below Havasu deeper layers and lateral translation of wells to spread the col- Creek, minimal change at Clear Creek, and increases in flow lective cone of depression resulting from a concentrated area at the south rim springs and Chevelon Creek of less than 0.1 of well withdrawals. and 0.3 ft3/s , respectively. Simulated changes in discharge for The CPWAC withdrawal scenarios primarily influence scenarios 2 and 3 are less because of lower rates of groundwa- water levels and groundwater discharge in the Coconino ter withdrawal with respect to scenario 1. Plateau basin, near the western margin of the Little Colorado Scenario 3 maintained the greatest simulated rates of River Plateau basin, and the Verde Valley subbasin. Simu- groundwater discharge to major streams and springs. The lated effects of the withdrawal scenarios are superimposed on scenario includes the importation of surface water for both effects of previous variations in groundwater withdrawals and tribal and nontribal demand in the CPWAC study area and artificial and incidental recharge. Effects of these pre-scenario reduced groundwater withdrawals. Scenario 3 resulted in variations include changes in water-levels in wells, groundwa- greater groundwater discharge than scenarios 1 and 2 at all ter storage, discharge to streams and springs, and evapotrans- major groundwater discharge features from 2006 through piration by plants that use groundwater. Future variations in 2105 except for Clear and Chevelon Creeks, where the same groundwater discharge will continue to occur as a result of the groundwater discharge was simulated by each of the three past changes. scenarios. Groundwater discharge to the Little Colorado River Water-level variations resulting from post-2005 ground- below Cameron was greatest for scenarios 2 and 3. Scenario 3 water withdrawals and incidental and artificial recharge in the resulted in almost no change in discharge after 2005. Scenario area of the withdrawal scenarios are primarily localized and 2 resulted in about 0.1 ft3/s loss in discharge by 2105. Greater superimposed on the regional changes caused by pre-2006 flows were simulated by scenario 3 in comparison to scenarios variations. Withdrawal scenario 1 produced a broad region on 1 and 2 at Havasu Creek, Colorado River below Havasu 30 Simulation of Groundwater Withdrawal Scenarios for the Redwall-Muav and Coconino Aquifer Systems of Arizona

Creek, south rim springs, Oak Creek above Page Springs, and Bills, D.J., Flynn, M.E., and Monroe, S.A., 2007, Hydrogeol- the upper Verde River. However, the increased flows in 2105 ogy of the Coconino Plateau and adjacent areas, Coconino in scenario 3 flows over scenario 2 were very small at all of and Yavapai Counties, Arizona: U.S. Geological Survey these features, less than about 0.1 ft3/s. Changes in groundwa- Scientific Investigations Report 2005–5222, 101 p., 4 pls. ter discharge will occur after 2105 to all major surface features that discharge from the Redwall-Muav and Coconino aquifers Bills, D.J., Truini, Margot, Flynn, M.E., Pierce, H.E., Catch- because change in aquifer storage was occurring at the end of ings, R.D., and Rymer, M.J., 2000, Hydrogeology of the the simulation in 2105. regional aquifer near Flagstaff, Arizona: U.S. Geological The accuracy of simulated changes resulting from the Survey Water-Resources Investigations Report 00–4122, CPWAC groundwater withdrawal scenarios is dependent on 143 p., 4 pls. the persistence of several hydrologic assumptions that are Blasch, K.W., Hoffmann, J.P., Graser, L.F., Bryson, J.R., and inherent in the NARGFM including, but not limited to, the Flint, A.L., 2006, Hydrogeology of the upper and middle reasonably accurate simulation of (1) transmissivity distribu- Verde River watersheds, central Arizona: U.S. Geological tions, (2) distributions of vertical hydraulic properties, (3) Survey Scientific Investigations Report 2005–5198, 101 p., distributions of spatial rates of withdrawal and incidental 3 pls. recharge, (4) aquifer extents, and (5) hydrologic barriers and conduits. The model can be improved with knowledge gained Bureau of Reclamation, 2006, C aquifer Water Supply study— from future investigations. Much of the hydrogeology in the Report of Findings: Bureau of Reclamation, Phoenix Area simulated area is poorly understood because of limited subsur- Office, Ariz., October 2006, 153 p., 6 appendices. face investigations and few long-term records of hydrologic change. The most prominent areas lacking hydrologic data Cooley, M.E., 1976, Spring flow from pre-Pennsylvanian include much of the Coconino Plateau basin, parts of the Little rocks in the southwestern part of the Navajo Indian Reser- Colorado River Plateau basin, and the Verde Valley subbasin. vation, Arizona: U.S. Geological Survey Professional Paper Future data collection in these areas, especially the Coconino 521-F, 15 p. Plateau basin, may alter the current understanding and simula- Cooley, M.E., Harshbarger, J.W., Akers, J.P., and Hardt, W.F., tion of the groundwater flow system in those areas. Accord- 1969, Regional hydrogeology of the Navajo and Hopi ingly, the hydrologic system simulated by the NARGFM Indian Reservations, Arizona, New Mexico, and Utah, with should not be considered a simulation of the true system, but a section on Vegetation, by O.N. Hicks: U.S. Geological a simulation of the system as it is currently understood and Survey Professional Paper 521–A, 61 p., 9 pls. simplified for simulation by using a numerical model. Errol L. Montgomery and Associates, 1999, Supplemental assessment of hydrogeologic conditions and potential effects of proposed groundwater withdrawal Coconino References Plateau Groundwater Sub-basin, Coconino County, Arizona June 1999: Appendix of the Final Environmental Impact Barlow, P.M., and Leake, S.A., 2012, Streamflow depletion by Statement for Tusayan Growth, Kaibab National Forest, wells—Understanding and managing the effects of ground- Williams, Arizona, July 1999, 256 p. water pumping on streamflow: U.S. Geological Survey Circular 1376, 84 p. Flint, L.E., and Flint, A.L., 2008, Regional analysis of ground- water recharge, in Stonestrom, D.A., Constantz, J., Ferré, Billingsley, G.H., 2000, Geologic map of the Grand Canyon T.P.A., and Leake, S.A., eds., Groundwater recharge in the 30’ x 60’ quadrangle, Coconino and Mohave Counties, arid and semiarid southwestern United States: U.S. Geologi- northwestern Arizona: U.S. Geological Survey Geologic cal Survey Professional Paper 1703, p. 29–59. Investigations Series I–2688, version 1.0, scale 1:100,000, 15 p. Gettings, M.E., and Bultman, M.W., 2005, Candidate-penetra- tive-fracture mapping of the Grand Canyon area, Arizona, Billingsley, G.H., Felger, T.L., and Priest, S.S., 2006, Geologic from spatial correlation of deep geophysical features and map of the Valle 30’ x 60’ quadrangle, Coconino County, surficial lineaments: U.S. Geological Survey Data Series Northern Arizona: U.S. Geological Survey Scientific Inves- DS–121, 1 DVD. tigations Map SIM 2895, scale 1:100,000, 27 p. Harbaugh, A.W., 2005, MODFLOW-2005 : The U.S. Geologi- Bills, D.J., and Flynn, M.E., 2002, Hydrogeologic data for the cal Survey modular ground-water model--the ground-water Coconino Plateau and adjacent areas, Coconino and Yavapai flow process: U.S. Geological Survey Techniques and Meth- Counties, Arizona: U.S. Geological Survey Open-File ods Report 6-A16, variously p. Report 02–265, 29 p. References 31

Harbaugh, A.W., Banta, E.R., Hill, M.C., and McDonald, Parker, J.T.C., Steinkampf, W.C., and, Flynn, M.E., 2005, M.G., 2000, MODFLOW-2000, The U.S. Geological Sur- Hydrogeology of the Mogollon Highlands, central Arizona: vey Modular Groundwater Model—User guide to modu- U.S. Geological Survey Scientific Investigations Report larization concepts and the groundwater flow process: U.S. 2004–5294, 87 p. Geological Survey Open-File Report 00-92, 121 p. Pool, D.R., Blasch, K.W., Callegary, J., and Glaser, L., 2011, Hart, R.J., Ward, J.J., Bills, D.J., and Flynn, M.E., 2002, Groundwater-flow model of the Redwall-Muav, Coconino, Generalized hydrogeology and groundwater budget for the and Alluvial Basin aquifer systems of northern and central Coconino aquifer, Little Colorado River Basin and parts of Arizona: U.S. Geological Survey Scientific Investigations the Verde and Salt River Basins, Arizona and New Mexico: Report 2010–5180, v. 1.1, 101 p. U.S. Geological Survey Water-Resources Investigations Report 02–4026, 47 p. Prudic, D.E., 1989, Documentation of a computer program to simulate stream-aquifer relations using a modular, finite-dif- Hoffmann, J.P., Bills, D.J., Phillips, J.V., and Halford, K.J., ference, ground-water flow model: U.S. Geological Survey 2005, Geologic, hydrologic, and chemical data from the Open-File Report 88–729, 113 p. C-aquifer near Leupp, Arizona: U.S. Geological Survey Scientific Investigations Report 2005–5280, 42 p. Ulrich, G.E., Billingsley, G.H., Hereford, Richard, Wolfe, E.W., Nealey, L.D., and Sutton, R.L, 1984, Map showing Huntoon, P.W., 1977, Relationship of tectonic structure geology, structure, and uranium deposits of the Flagstaff to aquifer mechanics in the western Grand Canyon dis- 1 x 2 degree quadrangle, Arizona: U.S. Geological Survey trict: Laramie, University of Wyoming, Water Resources Miscellaneous Investigations Series Map I–1446, scale, Research Institute, Water Resources Series no. 66, 51 p., 2 1:250,000. pls. U.S. Census Bureau, 2015, State and County Quick Facts: Kaczmarek, M.B., 2003, Investigation of groundwater avail- U.S. Census Bureau database, accessed February 26, 2015, ability for the Pine/Strawberry Water Improvement District: at http://quickfacts.census.gov/qfd/states/04/04005.htm. Helena, Montana, Morrison Maierle, 148 p. Winter, T.C., Harvey, J.W., Franke, O.L., and Alley, W.M., Leake, S.A., Hoffmann, J.P., and Dickinson, J.E., 2005, 1998, Ground water and surface water—a single resource: Numerical groundwater change model of the C-aquifer and U.S. Geological Survey Circular 1139, 79 p., accessed July effects of groundwater withdrawals on stream depletion in 14, 2010, at http://pubs.usgs.gov/circ/circ1139/. selected reaches of Clear Creek, Chevelon Creek, and the Little Colorado River, northeastern Arizona: U.S. Geologi- Wirt, Laurie, DeWitt, Ed, and Langenheim, V.E., 2005, Geo- cal Survey Scientific Investigations Report 2005–5277, 29 logic framework of aquifer units and groundwater flow- p. paths, Verde River headwaters, north-central Arizona: U.S. Geological Survey Open-File Report 2004–1411, variously Mann, L.J., 1976, Groundwater resources and water use in paged. southern Navajo County, Arizona: Arizona Water Commis- sion Bulletin 10, 106 p. Wolfe, E.W., Newhall, C.G., and Ulrich, G.E., 1987b, Geo- logic map of the northwest part of the San Francisco Vol- Mann, L.J., and Nemecek, E.A., 1983, Geohydrology and canic Field, north-central Arizona: U.S. Geological Survey water use in southern Apache County, Arizona: Arizona Miscellaneous Field Studies Map MF–1957, 2 sheets, scale, Department of Water Resources Bulletin 1, 86 p. 1:50,000. McGavock, E.H., Anderson, T.W., Moosburner, Otto, and Wolfe, E.W., Ulrich, G.E., Holm, R.F., Moore, R.B., and Mann, L.J., 1986, Water resources of southern Coconino Newhall, C.G., 1987a, Geologic map of the central part of County, Arizona: Arizona Department of Water Resources the San Francisco Volcanic Field, north-central Arizona: Bulletin 4, 53 p. U.S. Geological Survey Miscellaneous Field Studies Map MF–1959, 2 sheets, scale, 1:50,000. Monroe, S.A., Antweiler, R.C., Hart, R.J., Taylor, H.E., Truini, Margot, Rihs, J.R., and Felger, T.J., 2005, Chemical char- acteristics of groundwater discharge along the south rim of Grand Canyon in Grand Canyon National Park, Arizona, 2000–2001: U.S. Geological Survey Scientific Investiga- tions Report 2004–5146, 59 p. Appendixes Appendix 1 33 0 10 40 95 30 170 750 490 200 819 425 150 120 518 185 100 500 675 600 500 700 400 135 4,348 1,755 1,650 3,968 4,310 2050-2105 0 10 20 80 30 127 629 425 200 632 375 125 120 446 168 100 500 600 600 500 700 390 125 2040-2049 3,000 1,556 1,650 3,585 3,743 5 4 94 20 60 25 112 117 445 350 200 485 325 100 120 374 151 250 520 600 500 700 378 2030-2039 1,500 1,362 1,650 3,231 3,176 1 70 40 75 50 10 40 25 301 275 500 175 371 275 120 302 134 440 125 600 500 700 366 108 by simulated decade 2020-2029 Scenario 1 water use 1,168 1,650 2,954 2,607 0 0 4 0 9 34 50 60 10 20 99 23 117 196 200 175 230 225 230 974 360 125 600 700 354 2010-2019 1,650 2,700 2,042 0 0 0 0 0 0 0 0 26 75 25 50 90 20 169 200 170 196 200 781 280 100 570 274 342 2006-2009 2,576 2,701 1,475 /Coconino /Coconino 1 1 1 Aquifer Coconino Coconino Redwall Redwall-Muav Coconino Redwall-Muav Other Coconino Redwall Other Coconino Redwall-Muav Coconino Coconino Redwall-Muav Coconino Coconino Coconino Coconino Coconino Coconino Coconino Coconino Coconino Coconino Coconino Coconino Other

Water user Water Meadows) Water Company Water Hopi Tribe City of Flagstaff Canyon Mine Havasupai Tribe Navajo Tribe Tusayan Navajo Tribe Bellmont (Flagstaff Bellmont (Flagstaff Bearazona Wildlife Park Wildlife Bearazona Hualapai Tribe Hualapai Navajo Tribe Valle Doney Park Navajo Tribe City of Williams Flagstaff Ranch Flagstaff Forest Highlands Navajo Tribe Fox Ranch City of Flagstaff Fort Valley City of Flagstaff Kachina City of Flagstaff Mountainare Mountain Dell City of Flagstaff Parks

Area

(Flagstaff Meadows) (Flagstaff Dilkon, Red Lake, etc.) springs Company Moenkopi/Lower Moenkopi Canyon Mine Havasupai Cameron Tusayan Bodaway/Gap Bellmont Williams Hualapai Leupp Valle Doney Park Leupp wells (Seba Delka, Williams Flagstaff Ranch Flagstaff Forest Highlands Twin Arrows Casino Twin Fox Ranch Inner Basin wells and Fort Valley Lake Mary well field Kachina Woody Mountain well field Woody Mountainare Mountain Dell Water Local well field Parks Red Gap Ranch Groundwater demand scenario 1 developed by the Coconino Plateau Water Advisory Council for the period 2006–2105 including groundwater demand simulated Groundwater demand scenario 1 developed by the Coconino Plateau Water

Category Industrial Tribal, and Tribal, Municipal, withdrawals groundwater Appendix 1. for the Coconino and Redwall-Muav Aquifers using Northern Arizona Groundwater Flow Model (NARGFM) groundwater demand f or overlying disconnected aquifers that are not simulated using NARGFM. in acre-feet per year] [Values 34 Simulation of Groundwater Withdrawal Scenarios for the Redwall-Muav and Coconino Aquifer Systems of Arizona 410 815 497 275 410 946 5,648 7,366 2050-2105 32,644 25,278 340 675 362 230 340 946 2040-2049 4,379 5,917 27,708 21,791 270 535 265 163 270 457 2030-2039 simulated aquifers, but may discharge simulated aquifers, but may discharge 2,285 3,170 21,099 17,929 110 200 395 198 200 310 by simulated decade 2020-2029 Scenario 1 water use 2,603 3,221 17,998 14,777 98 70 130 255 130 203 2010-2019 1,623 1,994 13,696 11,702 64 62 125 250 125 175 2006-2009 1,393 1,694 12,514 10,820 - - /Redwall- 1 Aquifer Muav wall-Muav wall-Muav Other Coconino/Red Navajo Coconino/Red Navajo Navajo Navajo Water user Water Stock and domestic Stock and domestic Hopi Tribe Stock and domestic Navajo Tribe Navajo Tribe Navajo Tribe

Area area Williams to Grand Canyon Williams Flagstaff to Williams area Williams to Flagstaff Hopi Remaining area Coppermine LeChee Tuba City Tuba Groundwater demand scenario 1 developed by the Coconino Plateau Water Advisory Council for the period 2006–2105 including groundwater demand simulated Groundwater demand scenario 1 developed by the Coconino Plateau Water

Category Aquifers in younger rocks including those of local extent alluvial and volcanic that may be perched or hydraulically disconnected from the underlying 1 withdrawals withdrawals groundwater groundwater Other domes - tic, stock and Non-NARGFM small industrial groundwater to the simulated aquifers. simulated the to groundwater Total annual groundwater withdrawal Total Total annual NARGFM simulated groundwater withdrawal Total Annual withdrawals from aquifers not simulated using NARGFM Appendix 1. for the Coconino and Redwall-Muav Aquifers using Northern Arizona Groundwater Flow Model (NARGFM) groundwater demand f or overlying disconnected aquifers that are not simulated using NARGFM.—Continued. Appendix 2 35 0 0 0 0 10 40 95 30 200 518 500 500 700 490 425 185 675 120 150 100 600 400 135 1,650 3,968 4,310 4,348 1,755 2050-2105 0 0 0 0 10 20 80 30 200 446 500 500 700 425 375 168 600 120 125 100 600 390 125 2040-2049 1,650 3,585 3,743 3,000 1,556 0 0 0 5 4 20 60 25 112 117 200 374 250 500 700 350 325 151 520 120 100 600 378 2030-2039 1,650 3,231 3,176 1,500 1,362 0 0 0 1 50 40 75 10 40 25 175 302 500 700 275 275 134 440 120 500 125 600 366 108 2020-2029 1,650 2,954 2,607 1,168 by simulated decade Scenario 2 water use 0 0 0 0 9 0 4 0 60 50 10 20 99 23 117 175 200 230 700 225 360 974 125 600 354 2010-2019 1,650 2,700 2,042 0 0 0 0 0 0 0 0 26 75 50 25 90 20 170 169 200 196 200 274 280 781 100 570 342 2006-2009 2,576 2,701 1,475 ater Advisory Council for the period 2006–2105 including groundwater demand simulated /Coconino /Coconino 1 1 1 Aquifer Redwall-Muav Other Coconino Coconino Coconino Coconino Coconino Coconino Coconino Coconino Coconino Coconino Redwall-Muav Redwall-Muav Redwall-Muav Redwall Other Redwall Coconino Coconino Coconino Coconino Coconino Coconino Coconino Coconino Other Coconino

Water user Water Water Company Water Meadows) Havasupai Tribe Tribe Hualapai Hopi Tribe Navajo Tribe Navajo Tribe Navajo Tribe Navajo Tribe City of Flagstaff City of Flagstaff City of Flagstaff City of Flagstaff City of Flagstaff Tusayan Valle City of Williams Canyon Mine Navajo Tribe Park Wildlife Bearazona Doney Park Ranch Flagstaff Forest Highlands Fox Ranch Fort Valley Kachina Mountainare Mountain Dell Parks Bellmont (Flagstaff Bellmont (Flagstaff

Area

Dilkon, Red Lake, etc.) springs Company (Flagstaff Meadows) (Flagstaff Havasupai Hualapai Moenkopi/Lower Moenkopi Cameron Leupp Leupp wells (Seba Delka, Arrows Casino Twin Inner Basin wells and Lake Mary well field Mountain well field Woody Local well field Red Gap Ranch Tusayan Valle Williams Canyon Mine Bodaway/Gap Williams Bellmont Doney Park Ranch Flagstaff Forest Highlands Fox Ranch Fort Valley Kachina Mountainare Mountain Dell Water Parks Groundwater demand scenario 2 developed by the Coconino Plateau W

Category Industrial Tribal, and Tribal, Municipal, withdrawals groundwater Appendix 2. for the Coconino and Redwall-Muav Aquifers using Northern Arizona Groundwater Flow Model (NARGFM) groundwater demand f or overlying disconnected aquifers that are not simulated using NARGFM. in acre-feet per year] [Values 36 Simulation of Groundwater Withdrawal Scenarios for the Redwall-Muav and Coconino Aquifer Systems of Arizona 0 0 0 0 0 410 815 410 2050-2105 23,419 23,419 0 0 0 0 0 340 675 340 2040-2049 20,283 20,283 0 0 0 0 0 270 535 270 2030-2039 16,781 16,781 simulated aquifers, but may discharge simulated aquifers, but may discharge 0 0 0 0 0 200 395 200 2020-2029 by simulated decade Scenario 2 water use 13,875 13,875 0 0 0 0 0 130 255 130 2010-2019 11,178 11,178 64 62 175 125 250 125 2006-2009 1,694 1,393 12,514 10,820 - - ater Advisory Council for the period 2006–2105 including groundwater demand simulated /Redwall- 1 Aquifer Muav wall-Muav wall-Muav Navajo Navajo Navajo Navajo Coconino/Red Coconino/Red Other Water user Water Navajo Tribe Navajo Tribe Navajo Tribe Hopi Tribe Stock and domestic Stock and domestic Stock and domestic

Area area Coppermine LeChee City Tuba Hopi Flagstaff to Williams area Williams to Flagstaff Remaining area Williams to Grand Canyon Williams Groundwater demand scenario 2 developed by the Coconino Plateau W

Category Aquifers in younger rocks including those of local extent alluvial and volcanic that may be perched or hydraulically disconnected from the underlying 1 withdrawals withdrawals groundwater groundwater Other domes - tic, stock and Non-NARGFM small industrial Total annual groundwater withdrawal Total annual NARGFM simulated groundwater withdrawal Total Annual withdrawals from aquifers not simulated using NARGFM groundwater to the simulated aquifers. simulated the to groundwater Appendix 2. for the Coconino and Redwall-Muav Aquifers using Northern Arizona Groundwater Flow Model (NARGFM) groundwater demand f or overlying disconnected aquifers that are not simulated using NARGFM.—Continued. Appendix 3 37 0 0 0 0 0 10 30 95 40 200 700 500 500 425 185 518 490 120 135 400 600 100 150 2,500 3,968 1,650 1,755 4,348 2050-2105 0 0 0 0 0 10 30 80 20 200 700 500 500 375 168 446 425 120 125 390 600 100 125 2,500 3,585 1,650 1,556 3,000 2040-2049 0 0 0 0 5 4 25 60 20 117 112 200 700 500 250 325 151 374 350 120 378 600 100 2030-2039 2,500 3,231 1,650 1,362 1,500 0 0 0 0 1 50 40 25 40 10 75 175 700 500 275 134 302 275 120 108 366 600 125 500 2020-2029 2,500 2,954 1,650 1,168 by simulated decade Scenario 3 water use 0 9 0 0 0 0 4 0 60 23 99 20 10 50 117 175 700 360 225 200 230 354 600 125 974 2010-2019 2,042 2,700 1,650 0 0 0 0 0 0 0 0 26 50 75 20 90 25 170 274 280 169 200 196 200 342 570 100 781 2006-2009 1,475 2,701 2,576 ater Advisory Council for the period 2006– 2105 including groundwater demand simulated /Coconino /Coconino 1 1 1 Aquifer Other Redwall-Muav Coconino Coconino Coconino Coconino Coconino Coconino Coconino Redwall-Muav Redwall-Muav Redwall Coconino Redwall-Muav Coconino Coconino Other Redwall Other Coconino Coconino Coconino Coconino Coconino Coconino Coconino Coconino Coconino

Water user Water Water Company Water Meadows) Hualapai Tribe Hualapai Havasupai Tribe Hopi Tribe City of Flagstaff City of Flagstaff City of Flagstaff City of Flagstaff City of Flagstaff Navajo Tribe Valle City of Williams Canyon Mine Navajo Tribe Tusayan Navajo Tribe Navajo Tribe Navajo Tribe Bearazona Wildlife Park Wildlife Bearazona Parks Mountain Dell Mountainare Kachina Fort Valley Fox Ranch Forest Highlands Flagstaff Ranch Flagstaff Doney Park Bellmont (Flagstaff Bellmont (Flagstaff

Area

springs Dilkon, Red Lake, etc.) Company (Flagstaff Meadows) (Flagstaff Hualapai Havasupai Moenkopi/Lower Moenkopi Red Gap Ranch Local well field Woody Mountain well field Woody Lake Mary well field Inner Basin wells and Twin Arrows Casino Twin Valle Williams Canyon Mine Leupp wells (Seba Delka, Tusayan Cameron Leupp Bodaway/Gap Williams Parks Mountain Dell Water Mountain Dell Water Mountainare Kachina Fort Valley Fox Ranch Forest Highlands Flagstaff Ranch Flagstaff Doney Park Bellmont Groundwater demand scenario 3 developed by the Coconino Plateau W

Category Industrial Tribal, and Tribal, Municipal, withdrawals groundwater Appendix 3. for the Coconino and Redwall-Muav Aquifers using Northern Arizona Groundwater Flow Model (NARGFM) groundwater demand f or overlying disconnected aquifers that are not simulated using NARGFM. in acre-feet per year] [Values 38 Simulation of Groundwater Withdrawal Scenarios for the Redwall-Muav and Coconino Aquifer Systems of Arizona 0 0 0 0 0 410 815 410 2050-2105 20,934 20,934 0 0 0 0 0 340 675 340 2040-2049 18,440 18,440 0 0 0 0 0 270 535 270 2030-2039 15,585 15,585 simulated aquifers, but may discharge simulated aquifers, but may discharge 0 0 0 0 0 200 395 200 2020-2029 by simulated decade Scenario 3 water use 13,328 13,328 0 0 0 0 0 130 255 130 2010-2019 11,178 11,178 64 62 175 125 250 125 2006-2009 1,393 1,694 12,514 10,820 - - ater Advisory Council for the period 2006– 2105 including groundwater demand simulated /Redwall- 1 Aquifer wall-Muav wall-Muav Muav Other Navajo Navajo Navajo Navajo Coconino/Red Coconino/Red Water user Water Stock and domestic Navajo Tribe Navajo Tribe Navajo Tribe Hopi Tribe Stock and domestic Stock and domestic

Area area Williams to Grand Canyon Williams Coppermine LeChee City Tuba Hopi Remaining area Flagstaff to Williams area Williams to Flagstaff Groundwater demand scenario 3 developed by the Coconino Plateau W

Category Aquifers in younger rocks including those of local extent alluvial and volcanic that may be perched or hydraulically disconnected from the underlying 1 withdrawals withdrawals groundwater groundwater Other domes - tic, stock and Non-NARGFM small industrial groundwater to the simulated aquifers. simulated the to groundwater Total annual groundwater withdrawal Total Total annual NARGFM simulated groundwater withdrawal Total Annual withdrawals from aquifers not simulated using NARGFM Appendix 3. for the Coconino and Redwall-Muav Aquifers using Northern Arizona Groundwater Flow Model (NARGFM) groundwater demand f or overlying disconnected aquifers that are not simulated using NARGFM. Menlo Park Publishing Service Center, California Manuscript approval date August 3, 2016 Edited by Katherine Jacques Design and layout by Vivian Nguyen Pool—Simulation of Groundwater Withdrawal Scenarios for the Redwall-Muav and Coconino Aquifer Systems of Arizona—Scientific Investigations Report 2016–5115 ISSN 2328-0328 (online) http://dx.doi.org/10.3133/sir20165115